how to apply confirm dialog box from coding in asp.net with c#

By this we can open Confirmation Dialog box.........
============================>
          (on (---cs--)
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if (!IsPostBack)
        {
            Button3.Attributes.Add("onclick", "return cfrm();");
            Button4.Attributes.Add("onclick", "return cfrm();");
            Button5.Attributes.Add("onclick", "return cfrm();");
            Button6.Attributes.Add("onclick", "return cfrm();");
         
            Button7.Attributes.Add("onclick", "return cfrm();");
            Button10.Attributes.Add("onclick", "return cfrm();");
            Button11.AddAttributes.("onclick", "return cfrm();");
            MultiView1.ActiveViewIndex = 0;
        }

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============================
          (on (---aspx--)
---------------------------------------------------------------------------------------
<script language="javascript" type="text/javascript">
    function cfrm()
{
var x;
x=confirm('Are You Sure To Perform it!!!...');
if(x)
 return true;
else
return false;

}
</script>
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On Source-->
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<script language="javascript" type="text/javascript">
function cfrm()
{
var x;
x=confirm('Do you want to Confirm the Payout of select closing');
if(x)
 return true;
else
return false;

}
</script>
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On cs File-->
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protected void Page_Load(object sender, EventArgs e)
    {
        if (Session["admin"] == null)
        {
            Response.Redirect("~/AdminLogin.aspx");

        }

        if (!IsPostBack)
        {
            ddlbind();

            btn_ok.Attributes.Add("onclick", "return cfrm();");
        }
    }


protected void btn_ok_Click(object sender, EventArgs e)
     
    {
        con.update_data("update Payout set Flag=1 where         ComStep="+ddlclosing.SelectedValue+ "");
        RMG.Functions.MsgBox("Payout has been successfully confirmed");
        ddlbind();
    }
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