Sub Page_Load()
    Dim conn As New SqlConnection("connectionString");
    Dim cmd As New SqlCommand("SELECT Name, ID FROM Users", conn);
    Dim rdr As SqlDataReader
 
    Try
        conn.Open();
 
        rdr = conn.ExecuteReader()
 
        If rdr.HasRows Then
            dropdownlist1.DataSource = rdr
            dropdownlist1.DataBind()
        Else
            dropdownlist1.Items.Add(New ListItem("-- No values found --", "-- No values found --"))
        End If
    Catch ex As SqlException
        Response.Write(ex.ToString())
    Finally
        conn.Close();
    End Try
End Sub
 
Sub dropdownlist1_SelectedIndexChanged(s As Object, e As EventArgs) Handles dropdownlist1.SelectedIndexChanged
    Dim conn As New SqlConnection("connectionString");
    Dim cmd As New SqlCommand("SELECT Name, Address FROM Users WHERE ID=@id", conn);
    Dim rdr As SqlDataReader
 
    cmd.Parameters.AddWithValue("@id", dropdownlist1.SelectedValue)
 
    Try
        conn.Open();
 
        rdr = conn.ExecuteReader()
 
        If rdr.HasRows Then
            While rdr.Read()
                textbox1.Text = rdr("Name")
                textbox2.Text = rdr("Address")
            End While
        Else
            Response.Write("No users found with the given id: " & dropdownlist1.SelectedValue)
        End If
    Catch ex As SqlException
        Response.Write(ex.ToString())
    Finally
        conn.Close();
    End Try
End Sub
 
Sub button1_Click(s As Object, e As EventArgs)
    Dim conn As New SqlConnection("connectionString");
    Dim cmd As New SqlCommand("UPDATE Users SET Name=@name, Address=@address WHERE ID=@id", conn);
    Dim successfulRows As Integer = 0
 
    cmd.Parameters.AddWithValue("@name", Trim(textbox1.Text))
    cmd.Parameters.AddWithValue("@address", Trim(textbox2.Text))
    cmd.Parameters.AddWithValue("@id", dropdownlist1.SelectedValue)
 
    Try
        conn.Open();
 
        successfulRows = cmd.ExecuteNonQuery()
 
        If successfulRows > 0 Then
            Response.Write("Updated " & successfulRows & " successfully.")
        Else
            Response.Write("Could not find row to update with id: " & dropdownlist1.SelectedValue)
        End If
    Catch ex As SqlException
        Response.Write(ex.ToString())
    Finally
        conn.Close();
    End Try
End Sub