Check Valid Imag File

Hi Check file type and return true if its of gif, jpeg, pjpeg, png, jpg, bmp etc if it is of any other type then return false.

public static bool CheckValidJPGGIF(ref FileUpload file)
    {
        if (file.PostedFile.ContentType.ToLower() == "image/gif" || file.PostedFile.ContentType.ToLower() == "image/jpeg" || file.PostedFile.ContentType.ToLower() == "image/pjpeg" || file.PostedFile.ContentType.ToLower() == "image/x-png" || file.PostedFile.ContentType.ToLower() == "image/jpg" || file.PostedFile.ContentType.ToLower() == "image/bmp")
        {
            return true;
        }
        else
        {
            return false;
        }
    }