Working with database in Vb.net

Fig: Design (grey square is the gridview)

Source Code:

Imports System.Data
Imports System.Data.SqlClient

Public Class Database_Connectivity

    Dim conn As New SqlConnection("Data Source=.;Initial Catalog=practice ete;Integrated Security=True;Pooling=False")

'Inserting data

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        conn.Open()
        Dim str As String = "insert into Table1 values(@id,@name,@age,@phone)"
        'Dim str As String = "alter table Table1 add phone int"
        Dim comm As New SqlCommand()
        comm = New SqlCommand(str, conn)
        comm.Parameters.AddWithValue("@id", TextBox1.Text)
        comm.Parameters.AddWithValue("@name", TextBox2.Text)
        comm.Parameters.AddWithValue("@age", TextBox3.Text)
        comm.Parameters.AddWithValue("@phone", TextBox4.Text)
        comm.ExecuteNonQuery()
        MsgBox("Inserted")
        conn.Close()

    End Sub

'Deleting Data

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        conn.Open()
        Dim str As String = "delete from table1 where id=@id"
        Dim comm As New SqlCommand()
        comm = New SqlCommand(str, conn)
        comm.Parameters.AddWithValue("@id", TextBox1.Text)
        comm.ExecuteNonQuery()
        MsgBox("Record deleted")
        conn.Close()
    End Sub

'View Data

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        conn.Open()
        If (TextBox1.Text = "") Then
            Dim str As String = "select * from table1"
            Dim adapt As New SqlDataAdapter(str, conn)
            Dim ds As New DataSet
            adapt.Fill(ds)
            DataGridView1.DataSource = ds.Tables(0)
            conn.Close()
        End If


    End Sub


End Class