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Accepted
Vova Makarovych
Asked:2020-01-11 16:40:23 +0000 UTC2020-01-11 16:40:23 +0000 UTC

MySubstring 自己的函数

  • 772

我决定编写自己的函数 MySubstring。但是我不确定我是否做对了所有事情 + 在 main 它给出了一个我不能那样写的错误

string mySubstring = MySubstring(str1, 3, 3);

编码：

string MySubstring(string str, int startIndex, int length)
{
    string temp = System.String.Empty;
    for (int index = 0; index < str.Length; ++index)
    {
       if (str[index] == startIndex)
       {
          for (int j = 0; j < length; ++j)
          {
             temp += str[index];
          }
       }
    }
    return temp;
}
static void Main(string[] args)
{
   string str1 = "I like it like that";
   string mySubstring = MySubstring(str1, 3, 3);
   System.Console.WriteLine(mySubstring);
}
c#

1 个回答

  1. Best Answer

    您很可能会对扩展方法感兴趣。代码示例

    public static class StringExtensions
{
    public static string MySubstring(this string str, int startIndex, int length)
    {
        string temp = string.Empty;
        for (int index = 0; index < str.Length; ++index)
        {
            if (index == startIndex)
            {
                for (int j = index; j < length + index; ++j)
                {
                    temp += str[j];
                }
                return temp;
            }
        }
        return temp;
    }
}
class Program
{
    static void Main(string[] args)
    {
        string template = "привет мир!";
        var result = template.MySubstring(2, 5);
    }
}

    附言 如评论之一所述，为了不损失太多性能，您应该使用StringBuilder

    在 Program 类中创建方法的代码示例

    class Program
{
    static void Main(string[] args)
    {
        string template = "привет мир!";
        var result = MySubstring(template, 2, 5);
    }

    static string MySubstring(string str, int startIndex, int length)
    {
        string temp = string.Empty;
        for (int index = 0; index < str.Length; ++index)
        {
            if (index == startIndex)
            {
                for (int j = index; j < length + index; ++j)
                {
                    temp += str[j];
                }
                return temp;
            }
        }
        return temp;
    }
}

    附言 一个有效的（和正确的）方法看起来像这样

        static string MySubstring(string str, int startIndex, int length)
    {
        StringBuilder sb = new StringBuilder(length);

        for (int index = startIndex; index < length + startIndex; ++index)
        {
            sb.Append(str[index]);
        }
        return sb.ToString();
    }
    • 0

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