Revise paste vb,net

Imports System.Data.SqlClient
Public Class Form1
Dim connectionString As String=
"Data Source=(localdb)\MSSQLLocalDB;Integrated Security=True"
Dim connection As New SqlConnection(connectionString)
Dim cmd As SqlCommand
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles
MyBase.Load
connection.Open()
display()
End Sub
Private Sub Button4_Click(sender As Object, e As EventArgs) Handles
Button4.Click
'button add
txtid.Enabled = True
txtid.Focus()
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles
Button2.Click
'coding on remove button
delemp()
display()
End Sub
Private Sub Button3_Click(sender As Object, e As EventArgs) Handles
Button3.Click
'coding on update button
update_Stud()
display()
End Sub
Private Sub DataGridView1_CellClick(sender As Object, e As
DataGridViewCellEventArgs) Handles DataGridView1.CellClick
'coding on cell click event
'datagrid view
txtid.Enabled = False
Dim i As Integer
i = DataGridView1.CurrentRow.Index
If i = DataGridView1.RowCount - 1 Then
txtid.Text = DataGridView1.Item(0, i).Value
txtname.Text = DataGridView1.Item(1, i).Value
txtdesig.Text = DataGridView1.Item(2, i).Value
MsgBox("passed last record")
Else
txtid.Text = DataGridView1.Item(0, i).Value
txtname.Text = DataGridView1.Item(1, i).Value
txtdesig.Text = DataGridView1.Item(2, i).Value
End If
End Sub
Private Sub clear()
txtdesig.Text = ""
txtid.Text = ""
txtname.Text = ""
End Sub
Private Sub insertNew()
cmd = New SqlCommand("insert into Emp_3
values(@id,@name,@class)", connection)
cmd.Parameters.AddWithValue("@id", txtid.Text.Trim)
cmd.Parameters.AddWithValue("@name", txtname.Text.Trim)
cmd.Parameters.AddWithValue("@class", txtdesig.Text.Trim)
cmd.ExecuteNonQuery()
MsgBox("Record inserted successfully")
End Sub
Public Sub delemp()
Dim eid1 As Integer
id1 = InputBox("enter the reocrd to delete")
cmd = New SqlCommand("delete from Stud where id=@id", connection)
cmd.Parameters.AddWithValue("@id", id1)
cmd.ExecuteNonQuery()
MsgBox("record deleted successfully")
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles
Button1.Click
'coding on insert button
insertNew()
clear()
display()
End Sub
Public Sub display()
cmd = New SqlCommand("select * from Stud", connection)
cmd.ExecuteNonQuery()
Dim adpt As New SqlDataAdapter(cmd)
Dim ds As New DataSet()
adpt.Fill(ds, "studDS")
DataGridView1.DataSource = ds
DataGridView1.DataMember = "studDS"
End Sub
Public Sub update_stud()
cmd = New SqlCommand("update stud set
name=@name,class=@class where id=@id", connection)
cmd.Parameters.AddWithValue("@name", txtname.Text.Trim)
cmd.Parameters.AddWithValue("@class", txtdesig.Text.Trim)
cmd.Parameters.AddWithValue("@id", txtid.Text)
cmd.ExecuteNonQuery()
MsgBox("Record updated successfully")
End Sub
End Class