<script>
        $(':input').each(function () {
            switch (this.type) {
                case 'password':
                case 'text':
                case 'select-multiple':
                case 'select-one':
                case 'textarea':
                    $(this).val('');
                    break;
                case 'checkbox':
                case 'radio':
                    this.checked = false;
                    break;
            }
        });
</script>

ClearForm(Page.Form.Controls);

public void ClearForm(ControlCollection controls)
    {
        foreach (Control c in controls)
        {
            if (c.GetType() == typeof(System.Web.UI.WebControls.TextBox))
            {
                System.Web.UI.WebControls.TextBox t = (System.Web.UI.WebControls.TextBox)c;
                t.Text = String.Empty;
            }
            //... test for other controls in your forms DDL, checkboxes, etc.

            if (c.Controls.Count > 0) ClearForm(c.Controls);
        }
    }

foreach (Control i in Page.Form.GetAllChildren())
{
     if (i.GetType() == typeof(System.Web.UI.WebControls.TextBox))
     {
          System.Web.UI.WebControls.TextBox t = (System.Web.UI.WebControls.TextBox)i;
          t.Text = String.Empty;
     }
     // check other types
}

public static void ClearFields(ControlCollection pageControls)
    {
        foreach (Control contl in pageControls)
        {
            string strCntName = (contl.GetType()).Name;

            switch (strCntName)
            {
                case "TextBox":
                    TextBox tbSource = (TextBox)contl;
                    tbSource.Text = "";
                    break;
                case "RadioButtonList":
                    RadioButtonList rblSource = (RadioButtonList)contl;
                    rblSource.SelectedIndex = -1;
                    break;
                case "DropDownList":
                    DropDownList ddlSource = (DropDownList)contl;
                    ddlSource.SelectedIndex = -1;
                    break;
                case "ListBox":
                    ListBox lbsource = (ListBox)contl;
                    lbsource.SelectedIndex = -1;
                    break;
            }
            ClearFields(contl.Controls);
        }
    }
    protected void btn_cancel_Click(object sender, EventArgs e)
    {
        ClearFields(Form.Controls);
    }

ClearFields(Page.Form.Controls);