个人代码库のC#计算MD5和SHA1

using System;
namespace myMethod
{
class computeMD5andSHA1
{
/// <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 string MD5File(string fileName)
{
return HashFile(fileName , "md5");
}

/// <summary>
/// 计算文件的 sha1 值
/// </summary>
/// <param name="fileName">要计算 sha1 值的文件名和路径</param>
/// <returns>sha1 值16进制字符串</returns>
public string SHA1File(string fileName)
{
return HashFile(fileName , "sha1");
}

/// <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>
private 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>
private 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>
private string ByteArrayToHexString(byte[] buf)
{
return BitConverter.ToString(buf).Replace("-" , "");
}
}
}