StringBuilder 版本

public static string Md5_StringBuilder(string input)
{
    using var md5 = MD5.Create();
    var inputBytes = Encoding.UTF8.GetBytes(input);
    var hashBytes = md5.ComputeHash(inputBytes);
    var sb = new StringBuilder();
    foreach (var hashByte in hashBytes)
    {
        sb.Append(hashByte.ToString("X2"));
    }
    return sb.ToString();
}

BitConverter 版本

public static string Md5_BitConverter(string input)
{
    using var md5 = MD5.Create();
    var inputBytes = Encoding.UTF8.GetBytes(input);
    var hashBytes = md5.ComputeHash(inputBytes);
    return BitConverter.ToString(hashBytes).Replace("-", "");
}

StringConcat 版本

public static string Md5_StringConcat(string input)
{
    using var md5 = MD5.Create();
    var inputBytes = Encoding.UTF8.GetBytes(input);
    var hashBytes = md5.ComputeHash(inputBytes);
    var output = string.Empty;
    foreach (var hashByte in hashBytes)
    {
        output += hashByte.ToString("X2");
    }
    return output;
}

性能对比

先上我测试得到的数据(本机配置: 4 核 8 线程, 测试结果可能不一致)

看结果,的确是字符串拼接性能最差,但是 StringBuilder 好像也不是很高效啊,那个什么 Static 是啥玩意,怎么性能这么好,相对于 StringBuilder, 单线程性能提高了 3 倍, 多线性提高了 5 倍???

没错,这就是我要说的, 从 .net 5.0 开始提供了 2 个非常高效的方法

Convert.ToHexString
MD5.HashData

Convert.ToHexString 实例版本

public static string MD5_HexConvert_Instance(string input)
{
    using var md5 = MD5.Create();
    var inputBytes = Encoding.UTF8.GetBytes(input);
    var hashBytes = md5.ComputeHash(inputBytes);
    return Convert.ToHexString(hashBytes);
}

MD5.HashData 静态版本(强烈建议)

public static string MD5_HexConvert_Static(string input)
{
    var inputBytes = Encoding.UTF8.GetBytes(input);
    var hashBytes = MD5.HashData(inputBytes);
    return Convert.ToHexString(hashBytes);
}

总结

强烈建议 使用 MD5.HashData + Convert.ToHexString, 代码性能最高,也最简洁,只有 3 行
一定不要 忘记释放 MD5,我看网上很多在使用实例版本 MD5.Create() 后都没有 Dispose, 这会导致 内存泄漏!!!

最后放上我的完整的测试代码

using System.Text;
using System.Security.Cryptography;
using System.Diagnostics;

namespace ConsoleTest;

class Program
{
    public static string Md5_StringBuilder(string input)
    {
        using var md5 = MD5.Create();
        var inputBytes = Encoding.UTF8.GetBytes(input);
        var hashBytes = md5.ComputeHash(inputBytes);
        var sb = new StringBuilder();
        foreach (var hashByte in hashBytes)
        {
            sb.Append(hashByte.ToString("X2"));
        }
        return sb.ToString();
    }

    public static string Md5_StringConcat(string input)
    {
        using var md5 = MD5.Create();
        var inputBytes = Encoding.UTF8.GetBytes(input);
        var hashBytes = md5.ComputeHash(inputBytes);
        var output = string.Empty;
        foreach (var hashByte in hashBytes)
        {
            output += hashByte.ToString("X2");
        }
        return output;
    }

    public static string Md5_BitConverter(string input)
    {
        using var md5 = MD5.Create();
        var inputBytes = Encoding.UTF8.GetBytes(input);
        var hashBytes = md5.ComputeHash(inputBytes);
        return BitConverter.ToString(hashBytes).Replace("-", "");
    }

    public static string MD5_HexConvert_Instance(string input)
    {
        using var md5 = MD5.Create();
        var inputBytes = Encoding.UTF8.GetBytes(input);
        var hashBytes = md5.ComputeHash(inputBytes);
        return Convert.ToHexString(hashBytes);
    }

    public static string MD5_HexConvert_Static(string input)
    {
        var inputBytes = Encoding.UTF8.GetBytes(input);
        var hashBytes = MD5.HashData(inputBytes);
        return Convert.ToHexString(hashBytes);
    }

    private const int LOOPCOUNT = 100_0000;
    private static void CalcTime(Func<string, string> func, bool parallel = true)
    {
        Stopwatch stopwatch = Stopwatch.StartNew();

        if (parallel)
        {
            Parallel.For(0, LOOPCOUNT, i =>
            {
                func("123456");
            });
        }
        else
        {
            for (int i = 0; i < LOOPCOUNT; i++)
            {
                func("123456");
            }
        }

        stopwatch.Stop();
        Console.WriteLine($"{func.Method.Name,32}: {stopwatch.ElapsedMilliseconds,4}ms");
    }

    static void Main()
    {
        Test();

        Console.ReadKey();
    }

    private static void Test()
    {
        var functions = new List<Func<string, string>>
        {
            Md5_StringConcat,
            Md5_StringBuilder,
            Md5_BitConverter,
            MD5_HexConvert_Instance,
            MD5_HexConvert_Static,
        };

        foreach (var func in functions)
        {
            Console.WriteLine($"{func.Method.Name,32}: {func("123456")}");
        }

        Console.WriteLine($"\n单线程 {LOOPCOUNT} 次用时统计:");
        foreach (var func in functions)
        {
            CalcTime(func, false);
        }


        Console.WriteLine($"\n多线程 {LOOPCOUNT} 次用时统计:");
        foreach (var func in functions)
        {
            CalcTime(func, true);
        }
    }
}