[DotNetDevelopment] Confirm Dialog Box in ASP.net

[ASP.Net]

i am trying this:
Page.RegisterStartupScript(" ", " <script > if (confirm('You will lose
all the changes if not saved')==true){ ctlGridView.EditIndex = " +
e.NewEditIndex + ";} </script > ");

can anyone tell me why "ctlGridView.EditIndex =" is not getting the
value at runtime.