c# - String.Equals vs String.Compare vs "=="实战。需要解释

Question

以下是来自控制台应用程序的代码片段 -

class MyClass
{        
   public int GetDay(string data22)
    {
        int returnValue = 0;

        if (string.Compare(data22,"THURSDAY") == 0) // true
        {
            returnValue = (int)DayOfWeek.Thursday;
        }

        if (data22 == "THURSDAY") //false
        {
            returnValue = (int)DayOfWeek.Thursday;
        }

        if (string.Equals(data22, "THURSDAY"))//false
        {
            returnValue = (int)DayOfWeek.Thursday;
        }
        return returnValue;
    }
}

class Program
{
    static void Main(string[] args)
    {
        string ExecutionDay = "‎THURSDAY";
        MyClass obj1 = new MyClass();
        int MyDays = obj1.GetDay(ExecutionDay);
    }
}

问题是 - 为什么第一个比较 (string.compare) 有效而其他两种比较方法在这个特殊情况下不起作用？

Answer 1

Why does the first comparison (string.compare) work and the other two comparison methods does not work in THIS PARTICULAR CASE

您的代码中存在不可见字符(特别是 Left-to-Right mark(感谢@MatthewWatson))。您可以使用任何十六进制编辑器查看它们:

这被 string.Compare 忽略了，而 string.Equals 却没有。你可以在 the docs 中看到它:

Notes to Callers:

Character sets include ignorable characters. The Compare(String, String) method does not consider such characters when it performs a culture-sensitive comparison. For example, if the following code is run on the .NET Framework 4 or later, a culture-sensitive comparison of "animal" with "ani-mal" (using a soft hyphen, or U+00AD) indicates that the two strings are equivalent.