Why would string case comparison suddenly stop working in vb.net?

Question

Does anyone know how is the following possible? All of a sudden string comparison using .ToLower and Lcase stopped working.

If I do this in the immediate window:

?lcase(text)
"menu"
?lcase(text)="menu"
False

This just started a few minutes ago. I'm using:

.NET 4.5.2
Visual Studio 2013 Ultimate
Visual Basic

EDIT: The source of this problem is from here:Please how can i return decoded bytes instead of text from a CryptoStream

After making that code change.

the text being compared is got from UTF8.GetString(data) ... should this matter? — Charles Okwuagwu, May 25 '15 at 11:07
@CharlesO What is that default culture? What you have set in your regional settings in control panel? — Sriram Sakthivel, May 25 '15 at 11:10
A .net string is UTF-16, if you are binary comparing a UTF8 then there is the change of having differences. — the_lotus, May 25 '15 at 13:29

score 4 · Accepted Answer · answered May 25 '15 at 11:07

4

First of all, I would stop using LCase because it is VB 6 compability code.

Second I would not use .NETs build in "string".ToLower() or "string".ToUpper() in string comparisons because that can lead to some unexpected results for some locals.

Better use text.Equals("menu", StringComparison.OrdinalIgnoreCase)

I don't know what the root cause of your problem is, but hope that helps.

answered May 25 '15 at 11:07

Jürgen Steinblock

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the text being compared is got from UTF8.GetString(data) ... ill change all my string comparison to what you suggestion..tedious, but will take away the guessing game. Thanks. – Charles Okwuagwu May 25 '15 at 11:10
nope, no luck ?text.Equals("menu", StringComparison.OrdinalIgnoreCase) False – Charles Okwuagwu May 25 '15 at 11:12
text could contain unprintable chars, just a wild guess what is the output from `UTF8.GetBytes(text).Last().Equals(New Byte(0))`, if true, your string is NULL terminated which ist not common for .NET. – Jürgen Steinblock May 25 '15 at 11:15
?UTF8.GetBytes(text).Last().Equals(New Byte()) True – Charles Okwuagwu May 25 '15 at 11:17
?UTF8.GetBytes(text) {Length=16} (0): 77 (1): 101 (2): 110 (3): 117 (4): 0 (5): 0 (6): 0 (7): 0 (8): 0 (9): 0 (10): 0 (11): 0 (12): 0 (13): 0 (14): 0 (15): 0 – Charles Okwuagwu May 25 '15 at 11:19
ahh... the text is the result of a decryption. it seems the decypted bytes leaves empty bytes in the decryption buffer – Charles Okwuagwu May 25 '15 at 11:22
Try `text.TrimEnd(Convert.ToChar(0))` – Jürgen Steinblock May 25 '15 at 11:22
Thanks for the suggestion. It led me to the root of the problem. I had to remove the empty bytes left over from decrypting with CryptoStream – Charles Okwuagwu May 25 '15 at 14:24

score 0 · Answer 2 · answered May 27 '15 at 10:29

Take a look at String.Compare

'Declaration
Public Shared Function Compare ( _
    strA As String, _
    strB As String, _
    ignoreCase As Boolean _
) As Integer

Result Less than zero = strA is less than strB.
Result Zero = strA equals strB.
Result Greater than zero = strA is greater than strB.

Why would string case comparison suddenly stop working in vb.net?

2 Answers2