/**
* <summary>
* This Method gets the student data from the DB
* </summary>
*
* @method GetStudents
* @returns {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);
// bind the result in the GridView
StudentsGridView.DataSource = Students.AsQueryable().OrderBy(SortString).ToList();
StudentsGridView.DataBind();
}
}
protected void GetStudent()
{
// Populate the form with existing data
int StudentID = Convert.ToInt32(Request.QueryString["StudentID"]);
// Connect to the EF SB
using (ContosoConnection db = new ContosoConnection())
{
// Populate the Student Object instance with the Student id 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)
{
using (ContosoConnection db = new ContosoConnection())
{
// use the Student model to create a new student object and
// also save a new record
Student newStudent = new Student();
int StudentID = 0;
if (Request.QueryString.Count > 0) //our url has a sudentid in it
{
// Get the ID from the url
StudentID = Convert.ToInt32(Request.QueryString["StudentID"]);
//get the current student from the 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 the new student into the db
if (StudentID == 0)
{
db.Students.Add(newStudent);
}
//save the changes and our updates and inserts
db.SaveChanges();
//Redirect back to the students page
Response.Redirect("~/Contoso/Students.aspx");
}
}
/**
* <summary>
* This Event Handler deletes a student form the db using EF
* </summary>
*
* @methodStudentGridView_RowDeleting
* @param {object} sender
* @param {GridViewDeleteEventArgs} e
* @returns {void}
*/
protected void StudentsGridView_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
// store Which Row was clicked
int selectedRow = e.RowIndex;
// Get the selected StudentID using the grids data key collection
int StudentID = Convert.ToInt32(StudentsGridView.DataKeys[selectedRow].Values["StudentID"]);
// use EF to find the selected student from the db then remove it
using (ContosoConnection db = new ContosoConnection())
{
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 my changes back to the database
db.SaveChanges();
//Refresh the Grid
this.GetStudents();
}
}