实现时间表达式解析，到字符串17毫秒，到时间2毫秒。

public static class SimpleTimeSpanExpress

{

    /// <summary>

    /// 将TimeSpan转换为时间表达式。

    /// </summary>

    /// <param name="timeSpan"></param>

    /// <returns>时间表达式</returns>

    public static string ToString(TimeSpan timeSpan)

    {

        var result = string.Empty;

        if (timeSpan.Days > 0)

            result += $"{timeSpan.Days}d";

        result += Append(timeSpan.Days, "d");

        result += Append(timeSpan.Hours, "h");

        result += Append(timeSpan.Minutes, "m");

        result += Append(timeSpan.Seconds, "s");

        result += Append(timeSpan.Milliseconds, "ms");

        result += Append(timeSpan.Microseconds, "us");

        return result;

    }

    /// <summary>

    /// 从时间表达式转换到TimeSpan

    /// </summary>

    /// <param name="str"></param>

    /// <returns></returns>

    public static TimeSpan ToTimeSpan(string str)

    {

        var timespan = TimeSpan.Zero;

        timespan = timespan.Add(TimeSpan.FromDays(Parse(str, "d")));

        timespan = timespan.Add(TimeSpan.FromHours(Parse(str, "h")));

        timespan = timespan.Add(TimeSpan.FromMinutes(Parse(str, "m")));

        timespan = timespan.Add(TimeSpan.FromSeconds(Parse(str, "s")));

        timespan = timespan.Add(TimeSpan.FromMilliseconds(Parse(str, "ms")));

        timespan = timespan.Add(TimeSpan.FromMicroseconds(Parse(str, "us")));

        return timespan;

    }

    private static string Append(int value, string unit)

    {

        return value > 0 ? $"{value}{unit}" : string.Empty;

    }

    public static int Parse(string s, string unit)

    {

        var sliced = s.Split(unit);

        var str = Near(sliced[0]);

        if (int.TryParse(str, out var value))

        {

            return value < 0 ? throw new InvalidOperationException("值不能为负数。") : value;

        }

        throw new InvalidOperationException($"'{sliced[0]}' 不是一个有效的32位整数。");

    }

    private static string Near(string s)

    {

        var arr = new char[s.Length];

        var count = 0;

        for (var i = s.Length - 1; i >= 0; i--)

        {

            if (char.IsAsciiDigit(s[i]))

            {

                arr[i] = s[i];

                count++;

            }

            else

                break;

        }

        if (count == 0)

            throw new InvalidOperationException("只包含非数字字符串。");

        return new string(arr, arr.Length - count, count);

    }

}

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using JetBrains.Annotations;

using Microsoft.VisualStudio.TestTools.UnitTesting;

using System;

using JetBrains.Annotations;

using VideoSlice.Cli;

using Xunit;

using Assert = Xunit.Assert;

namespace VideoSlice.Tests;

{

    [Fact]

    public void METHOD()

    public void Should_ToString()

    {

        var time = new TimeSpan(1, 2, 3, 4, 5, 6);

        Assert.Equal("1d2h3m4s5ms6us", SimpleTimeSpanExpress.ToString(time));

    }

    [Fact]

    public void Should_ToTimeSpan()

    {

        var time = "1d2h3m4s5ms6us";

        Assert.Equal(new TimeSpan(1, 2, 3, 4, 5, 6), SimpleTimeSpanExpress.ToTimeSpan(time));

    }

}

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