/**
*<summary>
* This method gets the student data from the DB
* </summary>summary>
*
* @Method GetStudents
**/
protected void GetStudents()
{
//connect to EF
using (ContosoConnection db = new ContosoConnection())
{
string SortString = Session["SortColumn"].ToString() + " " + Session["SortDirection"].ToString();
//query the Students Table using EF and LINQ
var Students = (from allStudents in db.Students
select allStudents);
//bind the result to the GridView
StudentsGridView.DataSource = Students.AsQueryable().OrderBy(SortString).ToList();
StudentsGridView.DataBind();
}
}
protected void GetStudent()
{
//populate the form with existing data from the database
int StudentID = Convert.ToInt32(Request.QueryString["StudentID"]);
using (ContosoConnection db = new ContosoConnection())
{
//populate a student object instance with the StudentID from the URL Parameter
Student updatedStudent = (from student in db.Students
where student.StudentID == StudentID
select student).FirstOrDefault();
//map the student properties to the form controls
if (updatedStudent != null)
{
LastNameTextBox.Text = updatedStudent.LastName;
FirstNameTextBox.Text = updatedStudent.FirstMidName;
EnrollmentDateTextBox.Text = updatedStudent.EnrollmentDate.ToString("yyyy-MM-dd");
}
}
}
protected void SaveButton_Click(object sender, EventArgs e)
{
//connect to EF
using (ContosoConnection db = new ContosoConnection())
{
//use student model to create a new student object and save a new record
Student newStudent = new Student();
int StudentID = 0;
//url contains a student id
if (Request.QueryString.Count > 0)
{
//get id from url
StudentID = Convert.ToInt32(Request.QueryString["StudentID"]);
//get the current student from EF DB
newStudent = (from student in db.Students
where student.StudentID == StudentID
select student).FirstOrDefault();
}
//add data to the newStudent record
newStudent.LastName = LastNameTextBox.Text.ToString();
newStudent.FirstMidName = FirstNameTextBox.Text.ToString();
newStudent.EnrollmentDate = Convert.ToDateTime(EnrollmentDateTextBox.Text);
//use LINQ and ADO.NET to add / insert new student into the database
if (StudentID == 0)
{
db.Students.Add(newStudent);
}
//save changes - also updates and inserts
db.SaveChanges();
//redirect back to updated students page
Response.Redirect("~/Contoso/Students.aspx");
}
}
/// <summary>
/// This event handler deletes a student from the db using EF
/// </summary>
///
/// <param name="sender">{object} sender</param>
/// <param name="e">{GridViewDeleteEventArgs} e</param>
///
/// @method StudentsGridView_RowDeleting
protected void StudentsGridView_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
//store which row was clicked
int selectedRow = e.RowIndex;
//get the selected StudentID using the Grid's DataKey collection
int StudentID = Convert.ToInt32(StudentsGridView.DataKeys[selectedRow].Values["StudentID"]);
try
{
//use EF to find the selected student in the DB and remove it
using (ContosoConnection db = new ContosoConnection())
{
//create object of student class and store the query string inside of it
Student deletedStudent = (from studentRecords in db.Students
where studentRecords.StudentID == StudentID
select studentRecords).FirstOrDefault();
//remove the selected student from the db
db.Students.Remove(deletedStudent);
//save changes to db
db.SaveChanges();
//refresh the grid
this.GetStudents();
}
}
catch (Exception err)
{
//error message
}
}
