how to Refresh my datagridview in the windows form

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim cnn As New Odbc.OdbcConnection
        Dim cmd As New Odbc.OdbcCommand()
        Dim dr As Odbc.OdbcDataReader
        Try
            cnn.ConnectionString = "Dsn=class"
            cnn.Open()
            cmd = cnn.CreateCommand
            cmd.CommandText = "insert into customer(custno,custname,address,contactno,email) values(null,'" & TextBox1.Text & "','" & TextBox2.Text & "','" & TextBox3.Text & "','" & TextBox4.Text & "')"
            dr = cmd.ExecuteReader
            TextBox1.Text = " "
            TextBox2.Text = " "
            TextBox3.Text = " "
            TextBox4.Text = " "
            MsgBox("Success")
        Catch ex As Exception
            MsgBox("Error: " & ex.Source & " : " & ex.Message)
        End Try
    End Sub