A better approach (in your scenario) would be showing the window from code behind instead of calling a client function.
sender, EventArgs e)
Cause_Id = DtCause1.Rows.ToString();
// Set the VisibleOnPageLoad property to True
If you still want to call the client method, then follow the approach described in the KB Article and pass the parameter to the client method.
Calling radalert from codebehind
Do not hesitate to write again if you are experiencing any problem in implementing this.