Compare two strings in two different ways

Question

I've wrote this small program in C#

private void Form1_Load(object sender, EventArgs e)
{
    MessageBox.Show(("7797302D875A8922EBFC7DECBD352FE88F35642F" == "‎7797302D875A8922EBFC7DECBD352FE88F35642F").ToString());

    var a = "7797302D875A8922EBFC7DECBD352FE88F35642F";
    var b = "7797302D875A8922EBFC7DECBD352FE88F35642F";
    MessageBox.Show((a == b).ToString());

}

First messageBox shows "False" while Messagebox shows "True".

My question is: why can I not compare the two strings with the == operator?

possible duplicate of Are string.Equals() and == operator really same? — Gerald Versluis
– Gerald Versluis, Commented Jan 20, 2015 at 12:15
possible duplicate of C# .Equals(), .ReferenceEquals() and == operator — Rohit Prakash
– Rohit Prakash, Commented Jan 20, 2015 at 12:16
The == operator works just fine for strings. It's your second string literal that contains an invisible character at position 0, so it differs from the first string. — Pieter Witvoet
– Pieter Witvoet, Commented Jan 20, 2015 at 12:18
Also "7797302D875A8922EBFC7DECBD352FE88F35642F".Length == 40 && "‎7797302D875A8922EBFC7DECBD352FE88F35642F".Length == 41 — knittl
– knittl, Commented Jan 20, 2015 at 12:19

Soner Gönül · Accepted Answer · 2015-01-20 12:22:56Z

10

Your second string has invisible Left-to-right mark character as (U+200E).

Looks like just another copy-paste issue.

enter image description here

edited Jan 20, 2015 at 12:22

answered Jan 20, 2015 at 12:16

Soner Gönül

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3 Comments

Tim Schmelter Over a year ago

It might be important to note that you actually can use the == operator for strings.

Soner Gönül Over a year ago

@TimSchmelter Exactly. I didn't mentioned in my answer because this question already linked/closed as duplicate with stackoverflow.com/q/3678792/447156 and stackoverflow.com/q/814878/447156 in comments section. Also he can check it from reference source as well about how == overloaded for strings.

Jens Borrisholt Over a year ago

Thank you for your answer. Some how I didn't think of that my self :D

CodesInChaos · Accepted Answer · 2015-01-20 12:16:10Z

3

The difference isn't caused by the comparison, but your test string strings.

The second string of the first case starts with the invisible 0x200E, the unicode left-to-right mark.

answered Jan 20, 2015 at 12:16

CodesInChaos

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