为什么String.Equals返回false？

问题描述：

我有以下C＃代码（来自我正在使用的库），该代码试图查找比较指纹的证书。请注意，在以下代码中， mycert.Thumbprint 和 certificateThumbprint 都是字符串。

I have the following C# code (from a library I'm using) that tries to find a certificate comparing the thumbprint. Notice that in the following code both mycert.Thumbprint and certificateThumbprint are strings.

var certificateThumbprint = AppSettings.CertificateThumbprint;

var cert =
    myStore.Certificates.OfType<X509Certificate2>().FirstOrDefault(
      mycert => 
      mycert.Thumbprint != null && mycert.Thumbprint.Equals(certificateThumbprint)
      );

这无法找到带有指纹的证书，因为 mycert.Thumbprint.Equals （certificateThumbprint）是 false ，即使字符串相等。 mycert.Thumbprint == certificateThumbprint 也会返回 false ，而 mycert.Thumbprint.CompareTo（certificateThumbprint ）返回0。

This fails to find the certificate with the thumbprint because mycert.Thumbprint.Equals(certificateThumbprint) is false even when the strings are equal. mycert.Thumbprint == certificateThumbprint also returns false, while mycert.Thumbprint.CompareTo(certificateThumbprint) returns 0.

我可能遗漏了一些明显的内容，但我不知道为什么等于方法失败。

I might be missing something obvious, but I can't figure out why the Equals method is failing. Ideas?

答

比较要忽略某些字符：

static void Main(string[] args)
{
    var a = "asdas"+(char)847;//add a hidden character
    var b = "asdas";
    Console.WriteLine(a.Equals(b)); //false
    Console.WriteLine(a.CompareTo(b)); //0
    Console.WriteLine(a.Length); //6
    Console.WriteLine(b.Length); //5

   //watch window shows both a and b as "asdas"
}

（在这里，添加到 a 的字符是 U + 034F ，组合了Grapheme Joiner 。）

(Here, the character added to a is U+034F, Combining Grapheme Joiner.)

因此，CompareTo的结果不能很好地表明Equals中存在错误。您出现问题的最可能原因是隐藏字符。您可以检查长度以确保确定。

So CompareTo's result is not a good indicator of a bug in Equals. The most likely reason of your problem is hidden characters. You can check the lengths to be sure.

请参见此以获取更多信息。

See this for more info.

为什么String.Equals返回false？

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