C# string comparison failure

Question

My application is failing on a string comparison. I have put in a breakpoint and then used the intermediate window of Visual Studio and done the following experiment

subject

"<#MethodResourceObjectives>"

subject.Contains("<#Method")

true

subject.Contains("<#MethodResource")

true

subject.Contains("<#MethodResourceObjectives")

true

subject.Contains("<#MethodResourceObjectives>")

false

This would seem to be impossible, has anyone got a clue what could be happening?

Perhaps the ">" are different characters which have the same visual representation? — Codor
– Codor, Commented Jan 6, 2015 at 10:04
@joe, For fix to your issue, you can change the value(constant value) to which the subject value is compared with as it's containing unprintable characters, as mentioned by others. — Satyajit
– Satyajit, Commented Jan 6, 2015 at 10:45

Zoe - Save the data dump · Accepted Answer · 2019-05-24 21:29:45Z

57

It sounds like there may well be an unprintable character between the "s" and the ">".

I usually use something like this to show the true contents of a string:

for (int i = 0; i < text.Length; i++)
{
    Console.WriteLine("{0:x4}", (int) text[i]);
}

That's not as convenient from an immediate window, of course :(

In fact, just copying and pasting your text into my Unicode Explorer (at the bottom of the page), it looks like this is indeed the problem - you've got a U+200B (zero width space) before the >. You need to work out where that's coming from.

edited May 24, 2019 at 21:29

Zoe - Save the data dump

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answered Jan 6, 2015 at 10:03

Jon Skeet

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6 Comments

AndrewC Over a year ago

There is. I copied and pasted his string in to dotnetfiddle to check and there is a character before the > that shows up.

Sinatr Over a year ago

@leppie, why would subject.Contains("<#MethodResourceObjectives>") == false for any (printable/non-printable) symbol after > ?

leppie Over a year ago

@Sinatr: Because the constant string could have the unprintable character at the end and the test will fail.

Sinatr Over a year ago

@leppie, oh, you mean unprintable char in Contains function call itself. But than it can be anywhere in last test, because it's unprintable =P

Biniam Eyakem Over a year ago

s>"-s>" s%3E%22-s%u200B%3E%22

|

leppie · Accepted Answer · 2015-01-06 10:09:03Z

27

Doing a copy/paste of the text, I can confirm the same behavior.

Output:

"<#MethodResourceObjectives>".ToCharArray()
{char[27]}
    [0]: 60 '<'
    [1]: 35 '#'
    [2]: 77 'M'
    [3]: 101 'e'
    [4]: 116 't'
    [5]: 104 'h'
    [6]: 111 'o'
    [7]: 100 'd'
    [8]: 82 'R'
    [9]: 101 'e'
    [10]: 115 's'
    [11]: 111 'o'
    [12]: 117 'u'
    [13]: 114 'r'
    [14]: 99 'c'
    [15]: 101 'e'
    [16]: 79 'O'
    [17]: 98 'b'
    [18]: 106 'j'
    [19]: 101 'e'
    [20]: 99 'c'
    [21]: 116 't'
    [22]: 105 'i'
    [23]: 118 'v'
    [24]: 101 'e'
    [25]: 115 's'
    [26]: 62 '>'

Then

subject.ToCharArray()
{char[28]}
    [0]: 60 '<'
    [1]: 35 '#'
    [2]: 77 'M'
    [3]: 101 'e'
    [4]: 116 't'
    [5]: 104 'h'
    [6]: 111 'o'
    [7]: 100 'd'
    [8]: 82 'R'
    [9]: 101 'e'
    [10]: 115 's'
    [11]: 111 'o'
    [12]: 117 'u'
    [13]: 114 'r'
    [14]: 99 'c'
    [15]: 101 'e'
    [16]: 79 'O'
    [17]: 98 'b'
    [18]: 106 'j'
    [19]: 101 'e'
    [20]: 99 'c'
    [21]: 116 't'
    [22]: 105 'i'
    [23]: 118 'v'
    [24]: 101 'e'
    [25]: 115 's'
    [26]: 8203 ''  <--------- input string contains 'garbage'
    [27]: 62 '>'

answered Jan 6, 2015 at 10:09

community wiki

leppie

1 Comment

leppie Over a year ago

I added this as a community wiki as Jon Skeet already pointed out the issue. Was too long for a comment.

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