C# .NET 判断IO流是否图片

/// <summary>
/// 判断是否是图片
/// </summary>
public static bool IsPicture(Stream stream)
{
	try
	{
		byte[] buffer = new byte[2];
		stream.Read(buffer, 0, 2);
		string fileClass = buffer[0].ToString() + buffer[1].ToString();

		//255216是jpg;7173是gif;6677是BMP,13780是PNG;7790是exe,8297是rar   
		string[] fileType = { "255216", "7173", "13780", "6677" };
		return fileType.Contains(fileClass);
	}
	catch
	{
		return false;
	}
}