I am Prosenjit Muhury.
your solution given bellow.
string strscript="";
strscript = "<script language="javascript" type="text/javascript">";
strscript += " function confirm(){ window.alert('Upload Successfully');}";
strscript += "</script>";
Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "test", strscript);
ScriptManager.RegisterStartupScript(this, this.GetType(), "starScript", "confirm();", true);