c#计算文件的MD5值

/// <summary>
/// 计算文件的 MD5 值
/// </summary>
/// <param name="fileName">要计算 MD5 值的文件名和路径</param>
/// <returns>MD5 值16进制字符串</returns>
public static string MD5File(string fileName)
{
return HashFile(fileName, "md5");
} /// <summary>
/// 计算文件的哈希值
/// </summary>
/// <param name="fileName">要计算哈希值的文件名和路径</param>
/// <param name="algName">算法:sha1,md5</param>
/// <returns>哈希值16进制字符串</returns>
public static string HashFile(string fileName, string algName)
{
if (!System.IO.File.Exists(fileName))
return string.Empty; System.IO.FileStream fs = new System.IO.FileStream(fileName, System.IO.FileMode.Open, System.IO.FileAccess.Read);
byte[] hashBytes = HashData(fs, algName);
fs.Close();
return ByteArrayToHexString(hashBytes);
} /// <summary>
/// 计算哈希值
/// </summary>
/// <param name="stream">要计算哈希值的 Stream</param>
/// <param name="algName">算法:sha1,md5</param>
/// <returns>哈希值字节数组</returns>
public static byte[] HashData(System.IO.Stream stream, string algName)
{
System.Security.Cryptography.HashAlgorithm algorithm;
if (algName == null)
{
throw new ArgumentNullException("algName 不能为 null");
}
if (string.Compare(algName, "sha1", true) == 0)
{
algorithm = System.Security.Cryptography.SHA1.Create();
}
else
{
if (string.Compare(algName, "md5", true) != 0)
{
throw new Exception("algName 只能使用 sha1 或 md5");
}
algorithm = System.Security.Cryptography.MD5.Create();
}
return algorithm.ComputeHash(stream);
} /// <summary>
/// 字节数组转换为16进制表示的字符串
/// </summary>
public static string ByteArrayToHexString(byte[] buf)
{
string returnStr = "";
if (buf != null)
{
for (int i = 0; i < buf.Length; i++)
{
returnStr += buf[i].ToString("X2");
}
}
return returnStr;
}