`i have this code how can change the connection sql to Entity like NorthwindEntity`
```
> using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace Attendance_Management_System.PAL.User_Control
{
public partial class UserControlAttendance : UserControl
{
private string sql = @"Data Source = .\SQLEXPRESS;
Initial Catalog = Attendance_Management_System;
Integrated Security = True;";
private bool okay;
public UserControlAttendance()
{
InitializeComponent();
dataGridViewMarkAttendance.Columns["Column1"].Visible = false;
dataGridViewMarkAttendance.Columns["Column5"].Visible = false;
}
private void comboBoxClass_SelectedIndexChanged(object sender, EventArgs e)
{
if(Attendance.Attendance.IsMarkAttendance(dateTimePickerDate.Text, comboBoxClass.SelectedItem.ToString(), sql))
{
Attendance.Attendance.DisplayAndSearchAllData("SELECT Student_Table.Student_ID, Student_Name, Student_Reg, Attendance_Status FROM Student_Table INNER JOIN Attendance_Table ON Student_Table.Student_ID = Attendance_Table.Student_ID INNER JOIN Class_Table ON Class_Table.Class_ID = Student_Table.Class_ID WHERE Attendance_Date = '" + dateTimePickerDate.Text + "' AND Class_Name = '" + comboBoxClass.SelectedItem.ToString() + "';", dataGridViewMarkAttendance, sql);
okay = true;
}
else
{
Attendance.Attendance.DisplayAndSearchAllData("SELECT Student_ID, Student_Name, Student_Reg FROM Student_Table INNER JOIN Class_Table ON Class_Table.Class_ID = Student_Table.Class_ID WHERE Class_Name = '" + comboBoxClass.SelectedItem.ToString() + "';", dataGridViewMarkAttendance, sql);
okay = false;
}
}
private void tabPageMarkAttendance_Leave(object sender, EventArgs e)
{
if (comboBoxClass.SelectedIndex != -1)
{
if (comboBoxClass.SelectedIndex != -1)
{
string status;
if (Attendance.Attendance.IsMarkAttendance(dateTimePickerDate.Text, comboBoxClass.SelectedItem.ToString(), sql))
{
foreach (DataGridViewRow row in dataGridViewMarkAttendance.Rows)
{
if (Convert.ToBoolean(row.Cells["Column4"].EditedFormattedValue) == true)
status = "Present";
else
status = "Absent";
Attendance.Attendance.UpdateAttendance(row.Cells["Column1"].Value.ToString(), dateTimePickerDate.Text, status, sql);
}
}
else
{
foreach (DataGridViewRow row in dataGridViewMarkAttendance.Rows)
{
if (Convert.ToBoolean(row.Cells["Column4"].EditedFormattedValue) == true)
status = "Present";
else
status = "Absent";
Attendance.Attendance.MarkAttendance(row.Cells["Column1"].Value.ToString(), dateTimePickerDate.Text, status, sql);
}
}
}
}
}
private void dataGridViewMarkAttendance_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
{
if (comboBoxClass.SelectedIndex != -1)
{
if (Attendance.Attendance.IsMarkAttendance(dateTimePickerDate.Text, comboBoxClass.SelectedItem.ToString(), sql) && okay)
{
foreach (DataGridViewRow row in dataGridViewMarkAttendance.Rows)
{
if (row.Cells["Column5"].Value.ToString() == "Present")
row.Cells["Column4"].Value = true;
else
row.Cells["Column4"].Value = false;
}
}
}
}
private void comboBoxClass_Click(object sender, EventArgs e)
{
comboBoxClass.Items.Clear();
Attendance.Attendance.FillComboBox("SELECT DISTINCT(Class_Name) FROM Class_Table;", comboBoxClass, sql);
}
}
}
```
`i try this in combobox it,s working`
```
using(Attendance_Management_SystemEntities db=new Attendance_Management_SystemEntities())
{
db.Configuration.ProxyCreationEnabled = false;
comboBoxClass.DataSource = db.Class_Table.ToList();
comboBoxClass.ValueMember = "Class_ID";
comboBoxClass.DisplayMember = "Class_Name";
}
```
`but in private void comboBoxClass_SelectedIndexChanged not find way to do it`
What I have tried:
i try this in
<pre>private void ucAttendance_Load(object sender, EventArgs e)
{
using(Attendance_Management_SystemEntities db=new Attendance_Management_SystemEntities())
{
db.Configuration.ProxyCreationEnabled = false;
comboBoxClass.DataSource = db.Class_Table.ToList();
comboBoxClass.ValueMember = "Class_ID";
comboBoxClass.DisplayMember = "Class_Name";
}
}
work fine but in the combobox not work db
private void comboBoxClass_SelectedIndexChanged(object sender, EventArgs e)
{
if (Attendance.Attendance.IsMarkAttendance(dTPickerAttend.Text, comboBoxClass.SelectedItem.ToString(), ))
{
Attendance.Attendance.DisplayAndSearchAllData("SELECT Student_Table.Student_ID, Student_Name, Student_Reg, Attendance_Status FROM Student_Table INNER JOIN Attendance_Table ON Student_Table.Student_ID = Attendance_Table.Student_ID INNER JOIN Class_Table ON Class_Table.Class_ID = Student_Table.Class_ID WHERE Attendance_Date = '" + dTPickerAttend.Text + "' AND Class_Name = '" + comboBoxClass.SelectedItem.ToString() + "';", dataGridViewMarkAttendance, sql);
}
else
{
Attendance.Attendance.DisplayAndSearchAllData("SELECT Student_ID, Student_Name, Student_Reg FROM Student_Table INNER JOIN Class_Table ON Class_Table.Class_ID = Student_Table.Class_ID WHERE Class_Name = '" + comboBoxClass.SelectedItem.ToString() + "';", dataGridViewMarkAttendance, sql);
}
}