i want upload only jpg file in upload folder ?

if (FileUpload1.HasFile)
{
    string extension = System.IO.Path.GetExtension(FileUpload1.FileName);

    if (extension == ".jpg")
    {
        FileUpload1.SaveAs("yourpath" + FileUpload1.FileName);

    }
    else
    {
    Response.Write("Only .Jpg allowed");
    }
}