data table rowfilter (gridview filter)

protected void Button1_Click(object sender, EventArgs e)

{

DataTable dt = this.GridView1.DataSource as DataTable;


string filter = "field1='" + this.DropDownList1.SelectedItem.Text + "' AND " +

"field2='" + this.DropDownList2.SelectedItem.Text + "' AND " +

"field3='" + this.TextBox1.Text + "' AND " +

"field4='" + this.TextBox2.Text + "'";



dt.DefaultView.RowFilter = filter;

this.GridView1.DataBind();

}