protected void SaveButton_Click(object sender, EventArgs e)
{
//use EF to connect to server
using (ContosoConnection db = new ContosoConnection())
{
//use Stundent model to create new student object and save new record
Student newStudent = new Student();
int StudentID = 0;
//ou url has a student id
if (Request.QueryString.Count > 0)
{
//get the id from the 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 new student record
newStudent.LastName = LastNameTextBox.Text;
newStudent.FirstMidName = FirstNameTextBox.Text;
newStudent.EnrollmentDate = Convert.ToDateTime(EnrollmentDateTextBox.Text);
//use LINQ to ADO.NET to add/insert new student into the databasee
if (StudentID == 0)
{
db.Students.Add(newStudent);
}
//save our changes and updates and inserts
db.SaveChanges();
//redirect to updated students page
Response.Redirect("~/Contoso/Students.aspx");
}
}
/// <summary>
/// This method gets the student data from the DB
/// </summary>
/// @method GetStudents
/// @retuns {void}
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);
StudentsGridView.DataSource = Students.AsQueryable().OrderBy(SortString).ToList();
StudentsGridView.DataBind();
}
}
public List<cityPopulation> getCityPopulation()
{
List<cityPopulation> p = new List<cityPopulation>();
using (ContosoConnection db = new ContosoConnection())
{
var result = db.Departments.Select(x => new { x.Budget, x.Name });
result.ToList();
foreach (var res in result)
{
cityPopulation cpData = new cityPopulation();
cpData.city_name = res.Name.ToString();
cpData.population = Convert.ToInt32(res.Budget);
p.Add(cpData);
}
}
return p;
}
protected void GetStudent()
{
//populate the form with existing
int StudentID = Convert.ToInt32(Request.QueryString["StudentID"]);
//connect to EF DB
using (ContosoConnection db = new ContosoConnection())
{
//populate student object instance with the id from yhe URL parameter
Student updatedStudent = (from student in db.Students
where student.StudentID == StudentID
select student).FirstOrDefault();
if (updatedStudent != null)
{
LastNameTextBox.Text = updatedStudent.LastName;
FirstNameTextBox.Text = updatedStudent.FirstMidName;
EnrollmentDateTextBox.Text = updatedStudent.EnrollmentDate.ToString("yyyy-MM-dd");
}
}
}
/// <summary>
/// This event handler deletes students from the database using Entity Framework
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
protected void StudentsGridView_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
//show whic row was clicked
int selectedRow = e.RowIndex;
//get the selected StudentID uing the grids data key collections
int StudentID = Convert.ToInt32(StudentsGridView.DataKeys[selectedRow].Values["StudentID"]);
//use EF to find the selected student in the DB and remove it
using (ContosoConnection db = new ContosoConnection())
{
//create object of the student class and tore the query string inside it
Student deletedStudent = (from studentRecords in db.Students
where studentRecords.StudentID == StudentID
select studentRecords).FirstOrDefault();
//remove selected student
db.Students.Remove(deletedStudent);
// save my changes back to the database
db.SaveChanges();
//refresh grid
this.GetStudents();
}
}
