.net 实现得到文件夹中的图片文件

public bool IsPicture(string filePath)//filePath是文件的完整路径
{
try
{
System.IO.FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read);
BinaryReader reader = new BinaryReader(fs);
string fileClass;
byte buffer;
byte[] b = new byte[2];
buffer = reader.ReadByte();
b[0] = buffer;
fileClass = buffer.ToString();
buffer = reader.ReadByte();
b[1] = buffer;
fileClass += buffer.ToString();

reader.Close();
fs.Close();
if (fileClass == "255216 ")//255216是jpg;7173是gif;6677是BMP,13780是PNG;7790是exe,8297是rar
{
System.Console.Write(filePath);
return true;
}
else if (fileClass == "6677")
{
System.Console.Write(filePath);
return true;
}
else
{
return false;
}
}
catch
{
return false;
}
}