protected void Page_Load(object sender, EventArgs e)
{
//every time the page is processed (submitted to the
// web server) this method is the FIRST event
// that is processed that you can easily see and
// interaction with.
//this is a great place to do common code that is
// required on each process of the page
//Example: empty out old messages
//every control on your web form is a class instance
//every control has an ID property
//every control must have a unique name
//the ID value is used to reference the control in
// your code behind
//since controls are instances of a class, all rules
// of OOP apply
MessageLabel.Text = "";
//the web page has a flag that can be checked to see
// if the web page is posting back
if (!Page.IsPostBack)
{
//if the page is not PostBack, it means that this
// is the first time the page has been displayed
//you can do page initialization by testing the
// IsPostBack
//Create a List<T> where T is a class that has
// 2 columns: a value and a text display
List <DDLData> DataCollection = new List <DDLData>();
DataCollection.Add(new DDLData(1, "COMP1008"));
DataCollection.Add(new DDLData(3, "DMIT1508"));
DataCollection.Add(new DDLData(4, "DMIT2018"));
DataCollection.Add(new DDLData(2, "CPSC1517"));
//sorting a List<T>
// (x,y) are placeholders for 2 records at any given time in the sort
// => (lamda symbol) is part of the delegate syntax, read as "do the following"
// comparing x to y is ascending
// comparing y to x is descendinng
DataCollection.Sort((x, y) => x.displayField.CompareTo(y.displayField));
//place the data into the dropdownlist control
//a) assign the data collection to the "list" control
CollectionList.DataSource = DataCollection;
//b) this step is required for specific "list" controls
//indicate which data value is to be assigned to the Value field and the Display text field
//there are different styles in assigning this information
CollectionList.DataValueField = "valueField";
CollectionList.DataTextField = nameof(DDLData.displayField); //don's preference
//c)bind your data to the actual control
CollectionList.DataBind();
//d)OPTIONALLY you can place a prompt line on your control
CollectionList.Items.Insert(0, new ListItem("select....", "0"));
}
}
protected void Page_Load(object sender, EventArgs e)
{
//this method will execute on EACH and EVERY post back
//to this page.
//this method will execute on the first display of this page
//To determine if the page is new or postback use IsPostBack property
//this method is often used as a general method to reset
//fields or controls at the start of the page processing
//The label MessageLabel is used to display messages to the user
//Old messages should be remove from this control on each pass
//How does one reference a control on the .aspx form
//To reference a form control, use the control ID name
//EACH control is an object. THEREFORE alter a PROPERTY value.
MessageLabel.Text = "";
//Determine if this is the first display of the page
// and if so, load data into the dropdownlist
if (!Page.IsPostBack)
{
//Create an instance of List<T> for my "fake database" data
DataCollection = new List <DDLClass>();
//add data to the collection, one entry at a time
DataCollection.Add(new DDLClass(1, "COMP1008"));
DataCollection.Add(new DDLClass(2, "DMIT1508"));
DataCollection.Add(new DDLClass(3, "CPSC1517"));
DataCollection.Add(new DDLClass(4, "DMIT2018"));
//usually lists are sorted
//The List<T> has a .Sort() behaviour (method)
//(x,y) represents any two entries in the data collection at any point in time
// the lamda symbol => basically means "do the following"
//.CompareTo() is a method that will compare to items and return the result
// of comparing two items. The result is interpreted by the Sort() to
// to determine if the order needs to be changed.
// x vs y is ascending
// y vs x is descending
DataCollection.Sort((x, y) => x.DisplayField.CompareTo(y.DisplayField));
//place the collection into the dropdownlist
//a) assign the collection to the control (ID=CollectionList)
CollectionList.DataSource = DataCollection;
//b)assign the value and display portions of the dropdownlist
// to specify properties of the data class
CollectionList.DataTextField = nameof(DDLClass.DisplayField);
CollectionList.DataValueField = nameof(DDLClass.ValueField);
//c)Bind the data to the collection (physical attachment)
CollectionList.DataBind();
//d)You may wish to add a prompt line at the beginning of the
// list of data within the dropdownlist
CollectionList.Items.Insert(0, "select...");
}
}
protected void Page_Load(object sender, EventArgs e)
{
//this method executes BEFORE any event method on EACH processing of this web page
//this is a great place to do common code that is required on EACH process of the page
//Example: empty out old messages
Messagelabel.Text = "";
//this is an excellent place to do page initilization of controls for the first time
//checking the first time for the page uses the post back flag
//IsPostBack is a boolean value (true or false)
if (!Page.IsPostBack)
{
//if the page if not PostBack, it meanss that this if the first time the page has been displayed
//you can do page initalization
//create a collection of instances (class objects) that will be used to load the dropdownlist
//this will simulate the loading control as if the data can from a databases table
//each instance would represent a record on the database dataset
//to acomplish this simulation
List <DDLData> DDLCollection = new List <DDLData>();
DDLCollection.Add(new DDLData(1, "COMP1008"));
DDLCollection.Add(new DDLData(3, "DMIT1508"));
DDLCollection.Add(new DDLData(4, "DMIT2018"));
DDLCollection.Add(new DDLData(2, "CPSC1517"));
//place the data into the dropdownlist control
//4 steps to this process
//1) assign the data collection to the contorl
CollectionList.DataSource = DDLCollection;
//2) in this step, you will assign the value that will be displayed to the user and the value that will be associated
//and return from the control when the user picks a particular selection
//in the <select> control, this data was setup using the <option>
// <option value = "xxx"> display string </option>
//2 styles in setting up the control values
//A) a physical string of the field name
CollectionList.DataValueField = "ValueID";
//B) OOP style coding
CollectionList.DataTextField = nameof(DDLData.DisplayText);
//3) bind your data source to your control
CollectionList.DataBind();
//4) optional is to add a prompt list to your dropdownlist
CollectionList.Items.Insert(0, new ListItem("select...", "0"));
//sorting a List<T>
//(x,y) are place holder representing any 2 records at any given time druing the sort
//=> (lamda symbol) is part of the delegate syntax, I suggest that you read this symbol as "do the following"
//comparing x to y is ascending
//comparing y to x is descending
DDLCollection.Sort((x, y) => x.DisplayText.CompareTo(y.DisplayText));
}
}
protected void Page_Load(object sender, EventArgs e)
{
//this method is excuted automatically on each and every pass of the page (~kinda like IsPost)
//this method is executed BEFORE any event method on this page
//clear any old messages
OutputMessage.Text = "";
//this method is an excellant place to do page initialization
//you can test to post back on the page (IsPost)
// by checking Page.IsPostBack property
if (!Page.IsPostBack)
{
//the first time the page is processed
//create an intance of out list<t>
DataCollection = new List <DDLClass>();
//load the collection with a series of DDLCLASS instances
//create the instances using the greedy constuctor
DataCollection.Add(new DDLClass(1, "COMP1008"));
DataCollection.Add(new DDLClass(2, "CPSC1517"));
DataCollection.Add(new DDLClass(3, "DMIT2018"));
DataCollection.Add(new DDLClass(4, "DMIT1508"));
//use the list<t> method called .Sort to sort the contents of the list
// (x,y) the x and y represent two instances at any time in your collection
// x.field compared to y.field (ascending)
// y.field compared to x.field (decending)
DataCollection.Sort((x, y) => x.DisplayField.CompareTo(y.DisplayField));
//load the datacollection to the asp control you are interested in
// we are using the DropDownList
//a) assign you DataCollection to the control
CollectionList.DataSource = DataCollection;
//b) setup any necessary properties on your ASP control that are required to work
//the dropdown list will generate the html select tag code
// thus we need two properties to be set
// i)the value property DataValueField
// ii)the display property DataTextField
// the properties are set up by assigning the dataCollection field name to teh control property
CollectionList.DataValueField = "ValueField";
CollectionList.DataTextField = nameof(DDLClass.DisplayField);
// C) BIND your data to the control
CollectionList.DataBind();
// what about prompts?
// manually place a line item at the beginning of your control
CollectionList.Items.Insert(0, "select...");
}
}
protected void Page_Load(object sender, EventArgs e)
{
//this event method is executed EACH and EVERY time
// this page is processed
//this event method is executed BEFORE ANY EVENT method is processed
//clear out all old message
OutputMessage.Text = "";
//this page is an excellent place to do page initialization
// of your controls.
//there is a property to test for post back of your
// page called Page.IsPostBack (Razor: IsPost)
if (!Page.IsPostBack)
{
//do 1st page initialization processing
//create an instance of the data collection list
DataCollection = new List <DDLClass>();
//load the data collection with dummy data
//normally this data would come from your database
DataCollection.Add(new DDLClass(1, "COMP1008"));
DataCollection.Add(new DDLClass(2, "CPSC1517"));
DataCollection.Add(new DDLClass(3, "DMIT2018"));
DataCollection.Add(new DDLClass(4, "DMIT1508"));
//to sort a List<T> use the method .Sort()
//(x,y) x and y represent any two instances in your list at any time
//x.field compared to y.field : ascending
//y.field compared to x.field : descending
DataCollection.Sort((x, y) => x.DisplayField.CompareTo(y.DisplayField));
//setup the dropdownlist (radiobuttonlist, checkboxlist)
//a) assign your data to the control
CollectionList.DataSource = DataCollection;
//b) assign the data list field names to
// the appropriate control properties
// i) .DataValueField this is the value of the select option
// ii) .DataTextField this is the display of the select option
CollectionList.DataValueField = "ValueField";
CollectionList.DataTextField = nameof(DDLClass.DisplayField);
//c) phyiscally bind the data to the control for show
CollectionList.DataBind();
//what about a prompt?
//one can add a prompt to the start of the BOUND control list
//one will use the index 0 to position the prompt
CollectionList.Items.Insert(0, "select ....");
}
}
protected void Page_Load(object sender, EventArgs e)
{
//This method is executed automatically on EACH and EVERY pass of the page.
//This method is executed BEFORE ANY EVENT method on this page.
//clear any old messages
OutputMessage.Text = "";
//This method is an excellent place to do page initialization.
//You can test the postback of the page (Razor IsPost) by checking the Page.IsPostBack property.
if (!Page.IsPostBack)
{
//The first time the page is proccessed.
//Create an instance of the list of T.
DataCollection = new List <DDLClass>();
//Load the collection with a series of DDLClass instances. Create the instances using the greedy constructor.
DataCollection.Add(new DDLClass(1, "COMP1008"));
DataCollection.Add(new DDLClass(2, "CPSC1517"));
DataCollection.Add(new DDLClass(3, "DMIT2018"));
DataCollection.Add(new DDLClass(4, "DMIT1508"));
//When we use db's, this is the only thing that will be replaced.
//Use the List<T> method called .Sort to sort the contents of the list.
//(x,y) the x and y represent any 2 instances at any time in your collection.
//x.field compared to y.field (ascending)
//y.field compared to x.field (descending)
DataCollection.Sort((x, y) => x.DisplayField.CompareTo(y.DisplayField));
//=> is a Lambda expression, don't mix it up with >=!
//=> Means for X and Y, /do the following/, then specify what you want done.
//Load your data collection to the ASP control you are interested in: DropDownList
//Could also be done to a radio button list dynamically.
//A) Assign your data collection to the control.
CollectionList.DataSource = DataCollection;
//B) Setup any neccessary properties on your ASP control that are required to properly work.
//The dropdownlist will generate the HTML select tag code. Thus we need 2 properties to be set.
//i) Value property (DataValueField)
//ii) Display property (DataTextField)
//The properties are set up by assigning the data collection field name to the control property.
CollectionList.DataValueField = "ValueField";
CollectionList.DataTextField = nameof(DDLClass.DisplayField); //A way to do it without hardcoding the value.
//C) Bind your data to the control.
CollectionList.DataBind();
//What about prompts? Manually place a line item at the beginning of your control.
CollectionList.Items.Insert(0, "select ...");
}
}
protected void Page_Load(object sender, EventArgs e)
{
//This method will execute on each and every Postback to this page.
//This menthod will execute on the first display of this page
//To determine if the page is new or postback, use PostBack Property.
//This method is often used as a general method to reset fields or controls at the start of the page processing.
//E.g. The label MessageLabel is used to display messages to the user. Old messages should be removed from this control on each pass
// How does one reference a control on the .aspx form?
//To reference a form control, use the control ID name
//EACH CONTROL IS AN OBJECT. Therefore, ALTER A PROPERTY VALUE
MessageLabel.Text = "";
//Determine if this is the first display of the page, and if so, load data into the dropdownlist
if (!Page.IsPostBack)
{
//Create an instance of List<T> for my "Fake Database Data"
DataCollection = new List <DDLClass>();
//Add data to the collection, one entry at a time
DataCollection.Add(new DDLClass(1, "COMP1008"));
DataCollection.Add(new DDLClass(3, "DMIT1508"));
DataCollection.Add(new DDLClass(2, "CPSC1517"));
DataCollection.Add(new DDLClass(4, "DMIT2018"));
//usually lists are sorted
//The List<T> has a .Sort() behavior (method)
//(x,y) represent any two entries in the data collection at any point in time
//The landa symbol "=>" : basically means do the following
//.CompareTo() : is a method that would compare 2 items and return the result of the comparison.
//The result is interpreted by the Sort() to determine if the order needs to be changed.
// x vs y is ascending
// y vs x is descending
DataCollection.Sort((x, y) => x.DisplayField.CompareTo(y.DisplayField));
//Place the collection into the dropdown list
//a) assign the collection to the control (CollectionList)
CollectionList.DataSource = DataCollection;
//b) assign the value and display portions of the dropdownlist to specific properties of the data class
CollectionList.DataTextField = nameof(DDLClass.DisplayField);
CollectionList.DataValueField = nameof(DDLClass.ValueField);
//c) Bind the data to the collection (physical attachment)
CollectionList.DataBind();
//d) you may wish to add a prompt line at the beginning of the list of data within the dropdownlist
CollectionList.Items.Insert(0, "Select...");
}
}
protected void Page_Load(object sender, EventArgs e)
{
//Page_Load executes EACH AND EVERY time there is a posting
// to this page
//Page_Load is executed before any submit events
//this method is an excellent place to do form initialization
//you can test your postings using Page.IsPostBack
//IsPostBack is the same item as IsPost in our Razor forms
if (!Page.IsPostBack)
{
//this code will be executed only on the first pass
// to this page
//create an instance for the static data collection
DataCollection = new List <DDLClass>();
//Add instances to this collection using the DDLClass
// greedy constructor
DataCollection.Add(new DDLClass(1, "COMP1008"));
DataCollection.Add(new DDLClass(2, "CPSC1517"));
DataCollection.Add(new DDLClass(3, "DMIT2018"));
DataCollection.Add(new DDLClass(4, "DMIT1508"));
//sorting a list<t>
//use the .Sort() method
//(x,y) this represents any two items in your list
//compare x.Field to y.Field, ascending order
//compare y.Field to x.Field, descending order
DataCollection.Sort((x, y) => x.DisplayField.CompareTo(y.DisplayField));
//put the data collection into the drop down list
//a) assign the collection to the controls dataSource
CollectionList.DataSource = DataCollection;
//b) assign the field names to the properties of the
// drop down list for data association
//DataValueField represents the value of the item
//DataTextField represents the display of the line item
CollectionList.DataValueField = "ValueField";
CollectionList.DataTextField = nameof(DDLClass.DisplayField);
//c) bind the data to the web control
CollectionList.DataBind();
//can one put a prompt on the drop down list control?
// short answer: yes
CollectionList.Items.Insert(0, "select...");
}
}
protected void Page_Load(object sender, EventArgs e)
{
//if you need to reset fields on each pass (process) of the page
// you can do it here
//page initialization can be done here under the IsPostBack flag
//the ID= attribute on your control is the name that is use in
// your code to reference the control
//the ID= name is unique to the form
//each control is an object and behaves as an object
MessageLabel.Text = "";
//the test for posting a form back to the web server is IsPostBack
if (!Page.IsPostBack)
{
//load the DropDownList (DDL) only on the first pass of the page
//In this example a locally create List<T> will act
// as the data source for the DDL
DataCollection = new List <DDLClass>();
//add instances to the list
DataCollection.Add(new DDLClass(1, "COMP1008"));
DataCollection.Add(new DDLClass(2, "DMIT1508"));
DataCollection.Add(new DDLClass(3, "CPSC1517"));
DataCollection.Add(new DDLClass(4, "DMIT2018"));
//place the data in the DDL in alphabetic order (ascending)
//(x,y) represent any two rows in the collection DataCollection
//Compare x.DisplayField to y.DisplayField, ascending
//Compare y.DisplayField to x.DisplayField, descending
DataCollection.Sort((x, y) => x.DisplayField.CompareTo(y.DisplayField));
//to place a collection into the DDL control we need to do 4 steps
//a) assign the collection to the control's DataSource property
CollectionList.DataSource = DataCollection;
//b) assign field names to the properties DataTextField and DataValueField
//the DataTextField contents the data seen by the user
//the DataValueField is the data returned by the control on access*
CollectionList.DataTextField = "DisplayField";
CollectionList.DataValueField = "ValueField";
//c) Bind the information and data to your control
CollectionList.DataBind();
//d) optional, assign a prompt to your control
//such that it appears before the data
CollectionList.Items.Insert(0, "select....");
}
}
protected void Page_Load(object sender, EventArgs e)
{
//page load executes each and every time there is a posting to this page
//page load is executed before any submit events
//this method is and exelent place to do form initialization
// you can test your postings using Page.IsPostBack
//page.IsPostBack is the same as IsPost in our razor
if (!Page.IsPostBack)
{
//this code will be executed only on the first pass to this page
//create an instance for the static data collection
DataCollection = new List <DDLClass>();
//Add instances to this collection using the DDL gready constructor
DataCollection.Add(new DDLClass(1, "COMP1008"));
DataCollection.Add(new DDLClass(2, "CPSC1517"));
DataCollection.Add(new DDLClass(3, "DMIT2018"));
DataCollection.Add(new DDLClass(4, "DMIT1508"));
//Sorting a list of <T>
//using the .Sort() method
//(x,y) this represents any two items in your list
//Compare x.Field to y.Field; acending
//Compare y.field to x.field; decending
DataCollection.Sort((x, y) => x.DisplayField.CompareTo(y.DisplayField));
//put the data collection into the dropdown list
//a) assign the collection to the controls DataSource
CollectionList.DataSource = DataCollection;
//b) assign the field names to the properties of the drop down list for data association
//data value field represents the value of the item
//data text value represents the display value of the line item
CollectionList.DataValueField = "ValueField";
CollectionList.DataTextField = "DisplayField";
//CollectionList.DataTextField = nameof(DDLClass.DisplayField);
//c) bind the data to the web control
//NOTE: this statment is NOT required in a windows form application
CollectionList.DataBind();
//Can one put a promt on their drop down list control
//yes
CollectionList.Items.Insert(0, "select ...");
}
}
protected void Page_Load(object sender, EventArgs e)
{
//this method is executed each and every time you process this webpage
//this method executes before the event method
//this method is an excellent place to do initial form setup
//this method is an excellent place to change any control that may need to be done for the same action under all events
//example - clearing old messages
// a control is referenced in the code-behind by using its ID="controlname"
//Control names are global to all events
MessageLabel.Text = "";
//Assume you wish to do page intialization of some type but only one when the page is first loaded
if (!Page.IsPostBack)
{
DataCollection = new List <DDLClass>();
//load collection using greedy constructor and load to the list
DataCollection.Add(new DDLClass(1, "COMP1008"));
DataCollection.Add(new DDLClass(2, "CPSC1517"));
DataCollection.Add(new DDLClass(3, "DMIT1508"));
DataCollection.Add(new DDLClass(4, "DMIT2018"));
//List<T> can be sorted using .Sort(Delegate) Depending on your method, the delegate will be different.
//syntax for delegate
// (x,y) => x.PropertyName.CompareTo(y.PropertyName)
DataCollection.Sort((x, y) => x.DisplayField.CompareTo(y.DisplayField));
//attach the data to the dropdownlist control
//attach data
CollectionList.DataSource = DataCollection;
//assign the display text property to the ddl control - there are a couple of ways
//way THE FIRST
CollectionList.DataTextField = "DisplayField";
//WAY THE SECOND
//assign the value data property to the ddl control
CollectionList.DataValueField = nameof(DDLClass.ValueField);
//then do the databind thing
CollectionList.DataBind();
//optionally add a prompt line
CollectionList.Items.Insert(0, "Select ...");
}
}
protected void Page_Load(object sender, EventArgs e)
{
//Page_Load executes each and every time there is a posting
// to this page.
//Page_Load is executed before any submit events
//this method is an excellent place to do form initilizition
//You can Test your postings using Page.IsPostBack
//IsPostBack is the same item as IsPost in Razor Forms
if (!Page.IsPostBack)
{
//this code will be executed only on the first pass
// to this page
//create an instance for the static data collection
DataCollection = new List <DDLClass>();
//add instances to this collection using the DDLClass
// greedy constructor
DataCollection.Add(new DDLClass(1, "COMP1008"));
DataCollection.Add(new DDLClass(2, "CPSC1517"));
DataCollection.Add(new DDLClass(3, "DMIT2018"));
DataCollection.Add(new DDLClass(4, "DMIT1508"));
//sorting a List<T>
//use the .Sort() method
//(x,y) this represents any two items in your list
//compare x.Field to y.Field; ascending
//Compare y.Field to x.Field; descending
//=> lambda symbol. Think of it as Do the Following
DataCollection.Sort((x, y) => x.DisplayField.CompareTo(y.DisplayField));
//Put the data collection into the dropdownlist
//a) assign the collection to the controls DataSource
CollectionList.DataSource = DataCollection;
//b) assign the field names to the properties of the
// dropdownlist for data association
//DataValueField represents the value of the item
//DataTextField represents the display of the line item
CollectionList.DataValueField = "ValueField";
CollectionList.DataTextField = nameof(DDLClass.DisplayField);
//c) bind the data to the web control
//NOTE: This Statement is NOT required in a Windows Form Application
CollectionList.DataBind();
//Can one put a prompt on their dropdownlist control?
// Obvs, Yes.
CollectionList.Items.Insert(0, "Select...");
}
}
protected void Page_Load(object sender, EventArgs e)
{
// load empty feilds on first page refresh
Message.Text = "";
//------------------DROP DOWN LIST------------------------
//the web page has a flag that can be checked to see
// if the web page is posting back
if (!Page.IsPostBack)
{
//if the page is not PostBack, it means that this
// is the first time the page has been displayed
//you can do page initialization by testing the
// IsPostBack
// LIST is a bunch of the same classes
//Create a List<DDLdata> where T is a class that has
// 2 columns: a value and a text display
List <DDLData> ReviewStars = new List <DDLData>();
// adding values to the list
ReviewStars.Add(new DDLData(1, "1 star"));
ReviewStars.Add(new DDLData(2, "2 stars"));
ReviewStars.Add(new DDLData(3, "3 stars"));
ReviewStars.Add(new DDLData(4, "4 stars"));
ReviewStars.Add(new DDLData(5, "5 stars"));
// SORT
ReviewStars.Sort((x, y) => x.displayField.CompareTo(y.displayField));
// grab form id and place Review list into drop down list
CollectionList.DataSource = ReviewStars;
// if there is a value and text feild do this
CollectionList.DataValueField = "valueField";
CollectionList.DataTextField = nameof(DDLData.displayField);
//bind your data
CollectionList.DataBind();
// add in an insert
CollectionList.Items.Insert(0, new ListItem("select...", "0"));
}
}
protected void Page_Load(object sender, EventArgs e)
{
OutputMessage.Text = "";
//this event method is executed EACH and EVERY time this page is processed
//this event method is executed BEFORE ANY EVENT method is processed
//this page is an excellent place to do page initialization of your controls
//there is a property to test for post back of your page called Page.IsPostBack (Razor: IsPost)
if (!Page.IsPostBack)
{
//do 1st page initialization processing
//create an intence of the Data colletion list
DataCollection = new List <DDLClass>();
//load the data collection with dummy data, normally this data would com from your database
DataCollection.Add(new DDLClass(1, "Comp1008"));
DataCollection.Add(new DDLClass(2, "Cpsc1517"));
DataCollection.Add(new DDLClass(3, "Dmit2018"));
DataCollection.Add(new DDLClass(4, "Dmit1508"));
//to sort List<T> use the method .Sort()
//(x,y) x and y represent any two instances in your list at any time.
// x.firld compared to y.field : ascending
// y.field compared to x.field : desending
DataCollection.Sort((x, y) => x.DisplayField.CompareTo(y.DisplayField));
//setup the dropdown list
//a, assign your data to the control
CollectionList.DataSource = DataCollection;
//b, assign the data list field names to the approriate control properties
// i), .DatavalueField this is the value of the selection
// ii) .DataTextFiled this is the display of the selection optio
CollectionList.DataValueField = "ValueField";
CollectionList.DataTextField = nameof(DDLClass.DisplayField);
//bind the data to the control for show
CollectionList.DataBind();
//promt
//one can adda prompt to the start of the BOUND controllist
//one will use the index 0 to position the prompt
CollectionList.Items.Insert(0, "plese select");
}
}
protected void Page_Load(object sender, EventArgs e)
{
//Page_Load executes EACH AND EVERY TIME there is a posting to this page
//Page_Load is executed BEFORE any submit events
//this method is an excellent place to do form initialization. you can test your postings using Page.IsPostBack
//IsPostBack == IsPost() in Razor forms
//only executed on first pass, not ispost
//create an instance for the static data collection
if (!Page.IsPostBack)
{
DataCollection = new List <DDLClass>
{
//Add instances to this collection using the DDLClass greedy constructor
new DDLClass(1, "COMP1008"),
new DDLClass(2, "CPSC1517"),
new DDLClass(3, "DMIT2018"),
new DDLClass(4, "DMIT1508")
};
//sorting a List<T>
//use the .Sort() method
//(x,y) this represents any 2 items in your list
//compare x.Field to y.Field; ascending
//compare y.Field to x.Field; descending
DataCollection.Sort((x, y) => x.DisplayField.CompareTo(y.DisplayField));
//put the data collection into the dropdownlist (DDL)
//A) assign the collection to the controls DataSource
CollectionList.DataSource = DataCollection;
//B) assign the field names to the properties of the DDL for data association
//DataValueField represents the value of the item
//DataTextField represents the display of the line item
CollectionList.DataValueField = "ValueField";
CollectionList.DataTextField = "DisplayField";
//OR CollectionList.DataTextField = nameof(DDLCLass.DisplayField);
//C) bind the data to the web control
//NOTE: this statement is NOT required in a Windows Form Application
CollectionList.DataBind();
//you can put a prompt on their dropdownlist control
CollectionList.Items.Insert(0, "Select ...");
}//closes !Page.IsPostBack
}
protected void Page_Load(object sender, EventArgs e)
{
//Page_Load executes each and every time there is a posting to this page
//it is executed before any submit events
//This method is an exelent place to do form initialization
//you can test your postings using Page.IsPostBack
//IsPostBack is the same item as IsPost from the Razor forms
if (!Page.IsPostBack)
{
//create an instance for the static data collection
DataCollection = new List <DDLClass>();
//Add instance to this collection using the DDLClass greedy constructor
DataCollection.Add(new DDLClass(1, "COMP1008"));
DataCollection.Add(new DDLClass(2, "CPSC1517"));
DataCollection.Add(new DDLClass(3, "DMIT2018"));
DataCollection.Add(new DDLClass(4, "DMIT1508"));
//sorting a List<T>
//use the .sort()method
//(x,y) represents any 2 items in the list
//compare x.field to y.field; ascending
//if we compare y.field to x.field; descending
DataCollection.Sort((x, y) => x.DisplayField.CompareTo(y.DisplayField));
//put the data Collection into the drop down list
//a)assign the collection to the controls data source
CollectionList.DataSource = DataCollection;
//b) assign the field names through the properties of the drop down list for data association
//DateValueField rpresents the value fot he item
//DataTextField represents the display of the line item
CollectionList.DataValueField = "ValueField";
CollectionList.DataTextField = nameof(DDLClass.DisplayField);
//c)bind the data to the web control
//NOTE: This statement is not required in a windows form app
CollectionList.DataBind();
//can one put a prompt on their drowdownlist control
//yes
CollectionList.Items.Insert(0, "select ...");
}
}
//this method is executed every time the page is processed
//this event method is executed before any event method is processed
//this is a good place to do initialization of your controls
//there is a property to test for postback of your page
protected void Page_Load(object sender, EventArgs e)
{
//clear old messages
OutputMessage.Text = "";
if (!Page.IsPostBack)
{
//page init
DataCollection = new List <DDLClass>();
//load the data collection with dummy data
//normally this data would come from your database
DataCollection.Add(new DDLClass(1, "COMP1008"));
DataCollection.Add(new DDLClass(2, "CPSC1517"));
DataCollection.Add(new DDLClass(3, "DMIT2018"));
DataCollection.Add(new DDLClass(4, "DMIT1508"));
//sort arraylist
//(x,y)
//x.field compared to y.field = ascending
//y.field compared to x.field = decending
DataCollection.Sort((x, y) => x.DisplayField.CompareTo(y.DisplayField));
//setup the dropdown list (works for radiobutton or dropdown lists as well)
//a) assign your data to the control
CollectionList.DataSource = DataCollection;
//b) assign the data list field names to the appropriate control properties
// i) .DataValueField this is the value of the select option
// ii) .DataTextField this is the display of the select option
CollectionList.DataValueField = "ValueField";
CollectionList.DataTextField = nameof(DDLClass.DisplayField);
//c) physically bind the data to the control for show
CollectionList.DataBind();
//what about a prompt?
//one can add a prompt to the start of the BOUND control list
//one will use the index 0 to position the prompt
CollectionList.Items.Insert(0, "select...");
}
}
protected void Page_Load(object sender, EventArgs e)
{
//Every time the page is processed (submitted to the web server) this method is the FIRST event that is processed that you can easily see and interact with
//This is a great place to do common code that is required on each process of the page
//Example: empty out old messages
//Every Control on your web form is a class instance
//Every control has an ID property
//Every control must have a unique name
//The ID value is used to reference the control in your code behind
//Since controls are instances of a class, all rules of OOP apply
MessageLabel.Text = ""; //is the ID of the field that is shown on the bottom of the page (our output field)
//The web page has a flag that can be checked to see if the web page is posting back
if (!Page.IsPostBack)
{
//If the page is NOT PostBack, it means that this is the first time the page has been displayed
//You can do page initialization by testing the IsPostBack
//Create a List<T> where T is a class that has 2 columns: a value and a text display
//In die Klammer kommt die Type of objects (wo jetzt das T steht --> zb int oder float)
//Das T ist der Type of object, in diesem Fall ist der Type of object eine class die wir programmmiert haben ist oder build in ist
//int x
//List DataCollection
List <DDLData> DataCollection = new List <DDLData>(); //DataCollection is the name of the property in the Class Page called "DDL Data
DataCollection.Add(new DDLData(1, "COMP1008")); // new DDLData --> ist ein Object createn
DataCollection.Add(new DDLData(3, "DMIT1508"));
DataCollection.Add(new DDLData(4, "DMIT2018"));
DataCollection.Add(new DDLData(2, "CPSC1517"));
//Wir brauchen hierfuer einen Constructor weil wenn wir eine instance von ner object createn dann ist die Zahl und der Name required
//Wenn wir nix eingeben wuerden wuerde der leere constructor geurfen (nix in der Klammer)
//Sorting a List<T>
//(x,y) are placeholders for 2 records at any given time in the sort
// => (lamda symbol) is part of the delegate syntax, read as "do the following"
//Comparing x to y is ascending
//Comparing y to x is descending
DataCollection.Sort((x, y) => x.displayField.CompareTo(y.displayField));
//Place the data into the dropdownlist control
//a) assign the data collection to the "list" Control
CollectionList.DataSource = DataCollection; //CollectionList is the ID of the DROPDOWN and DataCollection of the List we created
//b) This step is required for specific "list" controls
//Indicate which data value is to be assigned to the Value field and the Display text field
//There are different styles in assigning this information
CollectionList.DataValueField = "valueField";
CollectionList.DataTextField = nameof(DDLData.displayField); //don's preference
//Other controls that handle lists we don't need B; we only need A and C
//c)Bind your data to the actual control
CollectionList.DataBind(); //CollectionList is the name of the Dropdown
//d)OPTIONALLY you can place a prompt line on your control
CollectionList.Items.Insert(0, new ListItem("Select...", "0")); //Die erste 0 ist die Stelle des Indexes (in diesem Falle an "1." Stelle)
//("Select...", "0") --> is a String and the Value (NOTE: we could also just put in the "Select..." without the Value)
}
}
protected void Page_Load(object sender, EventArgs e)
{
//this method executes BEFORE any event method on
// EACH processing of this web page
//this is a great place to do common code that is
// required on EACH process of the page
//Example: empty out old messages
MessageLabel.Text = "";
//this is an excellent place to do page initialization
// of controls on the 1st pass
//checking the 1st time for this page uses the post back flag
//Page.IsPostBack; this is a boolean value(true or false)
if (!Page.IsPostBack) //if(!false) => true
{
//if the page is not PostBack, it means that this
// is the 1st time the page has been displayed
//simulate the loading of the dropdownlist via a
// dataset from a database call
//create a collection of instances (class objects)
// that will be used to load the dropdownlist
//each instance will represent a record on the
// database dataset
//to accomplish is simulation, we will create a
// class and use it with a List<T>
//the <T> in this example is the class DDLData
List <DDLData> DDLCollection = new List <DDLData>();
DDLData aninstance = new DDLData();
aninstance.ValueId = 1;
aninstance.DisplayText = "COMP1008";
DDLCollection.Add(aninstance);
aninstance = new DDLData(3, "DMIT1508");
DDLCollection.Add(aninstance);
DDLCollection.Add(new DDLData(4, "DMIT2018"));
DDLCollection.Add(new DDLData(2, "CPSC1517"));
//sorting of a List<T
// (x,y) are placeholders representing any 2 records at any
// given time during the sort
// => (lamda symbol) is part of the delegate syntax, I suggest
// that you read this symbol as "do the following"
// comparing x to y is ascending
// comparing y to x is descending
DDLCollection.Sort((x, y) => x.DisplayText.CompareTo(y.DisplayText));
//place the data collection set into the dropdownlist control
//3 step to this process
//a) assign the data collection set to the control
CollectionList.DataSource = DDLCollection;
//b) in this step you will assign the value that will
// be diplayed to the user and the value that will
// be associated and return from the control wher
// the user picks a particular selection
//in the <select> control, this data was step using the <option>
// <option value="xxxx">display string</option>
//this information is assigned to the DDL control by use
// of the property name in your collection
//2 styles
// a) physical string of the field name
CollectionList.DataValueField = "ValueId";
// b) OOP style coding
CollectionList.DataTextField = nameof(DDLData.DisplayText);
//c) bind your data source to your control
CollectionList.DataBind();
//d) optionally
// add a prompt line to your dropdownlist
CollectionList.Items.Insert(0, new ListItem("select ...", "0"));
}
}
protected void Page_Load(object sender, EventArgs e)
{
// this method will execute on EACH and EVERY post back to this page
// this method will execute on the first display of this page
// to determine if the page is new or postback, use the IsPostBack property
// this method is often used as a general method to reset fields or controls at the start of page processing
// the label MessageLabel is used to display messages to the user. Old messages should be removed from this control on each pass
// how do we reference a control on the .aspx form? notice that each form control has an ID, we can use this.
// each control is an object, therefore we will be altering property values
MessageLabel.Text = "";
if (!Page.IsPostBack) // "!" means NOT
{
// here we are creating an instance of List<T> for the "fake database" data
DataCollection = new List <DDLClass>();
// add data to the collection that we just created, one entry at a time
DataCollection.Add(new DDLClass(1, "COMP1008"));
DataCollection.Add(new DDLClass(2, "DMIT1508"));
DataCollection.Add(new DDLClass(3, "CPSC1517"));
DataCollection.Add(new DDLClass(4, "DMIT2018"));
// one benefit of using a list vs an array is that we can easily sort them, we do this below using the .Sort() method
// (x, y) represents ANY two entries in the data collection at ANY point in time
// the lamda symbol "=>" basically means "do the following"
// .CompareTo() is a mehtod that will compare two items and return the result
// this result is then interpreted by the Sort() method to determind if the order needs to be changed
// x vs y is ascending
// y vs x is descending
DataCollection.Sort((x, y) => x.DisplayField.CompareTo(y.DisplayField));
// place the collection into the dropdownlist
// a) assign the collection to the control (ID = CollectionList
CollectionList.DataSource = DataCollection;
// b) assign the value and display portions of the dropdownlist to specify properties of the data class
CollectionList.DataTextField = nameof(DDLClass.DisplayField);
CollectionList.DataValueField = nameof(DDLClass.ValueField);
// c) bind the data to the collection (aka physical attachment)
CollectionList.DataBind();
// d) you may wish to add a prompt line at the beginning of the list of data within the dropdown list
CollectionList.Items.Insert(0, "select...");
}
} // closes PageLoad