private void FirePostBack()
{
     StringBuilder sbScript = new StringBuilder();
     sbScript.Append("<script language='JavaScript' type='text/javascript'>\n");
     sbScript.Append("<!--\n");
     sbScript.Append(ClientScript.GetPostBackEventReference(this, "PBArg") + ";\n");
     sbScript.Append("// -->\n");
     sbScript.Append("</script>\n");
     ClientScript.RegisterStartupScript(GetType(), "AutoPostBackScript", sbScript.ToString());
}

This code will execute a postback.

Cause a Postback in .NET

Net

C#