Confirmation message in C#(Server side)

Sample for

ScriptManager.RegisterStartupScript(this, typeof(string), "Message", "if(confirm('Source Code is already Existing.Do you want Overwrite?')){location.replace('default.aspx?" + param +"');}else{location.replace('CampaignTrack.aspx');}", true);

I redirected to another page with user input values as parameter values and did remaining process there.