Clearing the results of a datagrid from a page

[dougancil]

I have the following page and what I'd like to be able to do is that when the user clicks on the clear button that it disposes of the results of the datagridview and reloads the page. What would be the best way to go about doing that?

Imports System.Data.SqlClient
Imports System.Data
Partial Class _Default
    Inherits System.Web.UI.Page
    Protected Sub whosoncallButton_click(ByVal sender As Object, ByVal e As System.EventArgs) Handles whosoncallButton.Click
        Dim dt As New DataTable
        Dim da As New SqlDataAdapter
        Dim cmd As New SqlCommand
        Dim connectionString As String = "Initial Catalog=mdr;Data Source=xxxxx;uid=xxxxx;password=xxxxx"
        Dim con As New SqlConnection(connectionString)
        con.Open()
        cmd.Connection = con
        cmd.CommandType = CommandType.StoredProcedure
        cmd.CommandText = "getoncall"
        cmd.Parameters.AddWithValue("@subschedule", TextBox1.Text)
        Try
            da.SelectCommand = cmd
            da.Fill(dt)
            GridView1.DataSource = dt
            GridView1.DataBind()
            con.Dispose()
        Catch ex As Exception
            Response.Write("Error:" & ex.ToString)
        End Try
    End Sub

    Protected Sub clearButton_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles clearButton.Click
        TextBox1.Text = ""
        GridView1.DataSource = Nothing
    End Sub