CODEWITHSUNDEEP
c#stringcomparisonequality
Marius Bancila
Marius Bancila

Reputation: 16318

Why String.Equals is returning false?

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)
      );

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.

enter image description here

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

Upvotes: 27

Views: 11688

Answers (3)

brz
brz

Reputation: 6016

CompareTo ignores certain characters:

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"
}

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

Debug mode

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.

See this for more info.

Upvotes: 23

Subhash
Subhash

Reputation: 51

Sometimes when we insert data in database it stores some spaces like "question ". And when you will try to compare it with "question" it returns false. So my suggestion is: please check the value in database or use Trim() method.

In your case, please try: mycert.Thumbprint != null && mycert.Thumbprint.trim().equals(certificateThumbprint.trim())

I think it will return true if any record will exist.

Upvotes: 0

AperioOculus
AperioOculus

Reputation: 6821

You may wish to try using an overload of String.Equals that accepts a parameter of type StringComparison.

For example:

myCert.Thumbprint.Equals(certificateThumbprint, StringComparison.[SomeEnumeration])


Where [SomeEnumeration] is replaced with one of the following enumerated constants:

 - CurrentCulture
 - CurrentCultureIgnoreCase
 - InvariantCulture
 - InvariantCultureIgnoreCase
 - Ordinal
 - OrdinalIgnoreCase


Reference the MSDN Documentation found here. enter image description here

Upvotes: 2

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