How to empty all TextBoxes of the page at one shot?

Write following function in the common class.

public class MyClass
{
public static void ResetTextBoxes(Control oControl)
    {
        foreach (Control c in oControl.Controls)
        {
            if (c is TextBox)
            {
                TextBox t = (TextBox)c.FindControl(c.ID);
                t.Text = string.Empty;
            }
            if (c.HasControls())
            {
                ResetTextBoxes(c);
            }
        }
    }//ResetTextBoxes
}

Call the above function like this

MyClass. ResetTextBoxes(this);

You should ensure that you are using following namespace in the class file where you are writing this function
using System;
using System.Web.UI.WebControls;
using System.Web.UI;
using System.Web;