这是用于反向字符串的代码

public Static void main(){
    string text = "Test Text";
    Console.Writeline(RevestString(text))
}

public Static string RevestString(string text){
    char[] textToChar = text.ToCharArray();
    string result= string.Empty;
    int length = textToChar .Length;
    for (int i = length; i > 0; --i)
    result += textToChar[i - 1];
    return result;
}

我从Microsoft.VisualBasic.Strings中做了一个c#移植。我不知道他们为什么把这么有用的函数(从VB)保存在系统之外。框架中的字符串，但仍然在Microsoft.VisualBasic下。同样的场景用于财务函数(例如microsoft . visualbasic . finance . pmt())。

public static string StrReverse(this string expression)
{
    if ((expression == null))
        return "";

    int srcIndex;

    var length = expression.Length;
    if (length == 0)
        return "";

    //CONSIDER: Get System.String to add a surrogate aware Reverse method

    //Detect if there are any graphemes that need special handling
    for (srcIndex = 0; srcIndex <= length - 1; srcIndex++)
    {
        var ch = expression[srcIndex];
        var uc = char.GetUnicodeCategory(ch);
        if (uc == UnicodeCategory.Surrogate || uc == UnicodeCategory.NonSpacingMark || uc == UnicodeCategory.SpacingCombiningMark || uc == UnicodeCategory.EnclosingMark)
        {
            //Need to use special handling
            return InternalStrReverse(expression, srcIndex, length);
        }
    }

    var chars = expression.ToCharArray();
    Array.Reverse(chars);
    return new string(chars);
}

///<remarks>This routine handles reversing Strings containing graphemes
/// GRAPHEME: a text element that is displayed as a single character</remarks>
private static string InternalStrReverse(string expression, int srcIndex, int length)
{
    //This code can only be hit one time
    var sb = new StringBuilder(length) { Length = length };

    var textEnum = StringInfo.GetTextElementEnumerator(expression, srcIndex);

    //Init enumerator position
    if (!textEnum.MoveNext())
    {
        return "";
    }

    var lastSrcIndex = 0;
    var destIndex = length - 1;

    //Copy up the first surrogate found
    while (lastSrcIndex < srcIndex)
    {
        sb[destIndex] = expression[lastSrcIndex];
        destIndex -= 1;
        lastSrcIndex += 1;
    }

    //Now iterate through the text elements and copy them to the reversed string
    var nextSrcIndex = textEnum.ElementIndex;

    while (destIndex >= 0)
    {
        srcIndex = nextSrcIndex;

        //Move to next element
        nextSrcIndex = (textEnum.MoveNext()) ? textEnum.ElementIndex : length;
        lastSrcIndex = nextSrcIndex - 1;

        while (lastSrcIndex >= srcIndex)
        {
            sb[destIndex] = expression[lastSrcIndex];
            destIndex -= 1;
            lastSrcIndex -= 1;
        }
    }

    return sb.ToString();
}

private static string Reverse(string str)
        {
            string revStr = string.Empty;
            for (int i = str.Length - 1; i >= 0; i--)
            {
                revStr += str[i].ToString();
            }
            return revStr;
        }

比上述方法快

private static string ReverseEx(string str)
        {
            char[] chrArray = str.ToCharArray();
            int len = chrArray.Length - 1;
            char rev = 'n';
            for (int i = 0; i <= len/2; i++)
            {
                rev = chrArray[i];
                chrArray[i] = chrArray[len - i];
                chrArray[len - i] = rev;
            }
            return new string(chrArray);
        }

如何:

    private string Reverse(string stringToReverse)
    {
        char[] rev = stringToReverse.Reverse().ToArray();
        return new string(rev); 
    }

在使用StringInfo.GetTextElementEnumerator()的地方有几个正确答案。向你致敬!

现在，让我们找出最有效的方法来使用这个方法。首先，大多数答案涉及调用Reverse()和ToArray()，这在热路径上是一个大禁忌。为了获得最佳性能，我们希望避免分配垃圾。例如，临时字符串，分配器，数组等。

优化的管柱反转

降低气相色谱压力。也就是说，没有LINQ枚举器，没有数组。 使用跨 使用String.Create ()

using System.Globalization;

public static class StringExtensions
{
    public static string AsReversed(this string s)
    {
        return string.Create(s.Length, s, (chars, state) =>
        {
            int i = 0;
            var enumerator = StringInfo.GetTextElementEnumerator(s);
            while (enumerator.MoveNext())
            {
                var element = enumerator.GetTextElement();
                i += element.Length;
                element.CopyTo(chars[^i..]);
            }
        });
    }
}

请注意，GetTextElementEnumerator() API在. net Core 3.1和更早的版本中包含一个错误。确保运行。net 5或更高版本!最后，请务必查看正在讨论API改进的问题#19423。

非常简单

static void Reverse()
    {
        string str = "PankajRawat";
        var arr = str.ToCharArray();
        for (int i = str.Length-1; i >= 0; i--)
        {
            Console.Write(arr[i]);
        }
    }