how to clear multiple no of textboxes

Try this:

make a method like this:

private void ClearFormControlValues(Control parent)
        {
            foreach (Control c in parent.Controls)
            {
                if (c.Controls.Count > 0)
                {
                    ResetFormControlValues(c);
                }
                else
                {
                    switch (c.GetType().ToString())
                    {
                        case "System.Web.UI.WebControls.TextBox":
                            ((TextBox)c).Text = "";
                            break;
                        case "System.Web.UI.WebControls.CheckBox":
                            ((CheckBox)c).Checked = false;
                            break;
                        case "System.Web.UI.WebControls.RadioButton":
                            ((RadioButton)c).Checked = false;
                            break;

                    }
                }
            }
        }

And call this method on button click or any other event you want like this:

protected void submit_Click(object sender, EventArgs e)
{
     ClearFormControlValues(this);
}

this will clear all the textboxes, checkboxes & radio buttons on your form, you can remove checkbox and radiobutton if you want only textboxes to clear, in the same way you can add more control.

hope it helps :)