Fix empty strings in ThrowHelper

[elachlan]

Replacing empty strings with string.Empty

I ran into this as msbuild relies on Microsoft.CodeAnalysis.Collections and the stylecop analyzer highlighted this problem when we turned on the rule SA1122.

The associated msbuild PR is dotnet/msbuild#7239

[CyrusNajmabadi]

I don't really get the purpose of this rule.

[elachlan]

I don't really get the purpose of this rule.

As far as I know, it's supposed to reduce string allocations.

[CyrusNajmabadi]

String literals are already interned. So using "" is not going to be an allocation problem :-)

[elachlan]

Based on my reading, the advantage is in readability and to reduce the chance of a hidden zero width space character.

There was acutally one disadvantage that I saw:
"Another difference is that String.Empty generates larger CIL code"
https://stackoverflow.com/a/17386465/908889

It also isn't a constant:
https://stackoverflow.com/questions/507923/why-isnt-string-empty-a-constant
Which results in some usages being incorrect:
https://stackoverflow.com/a/13703103/908889

I will take this to MSBuild and Stylecop and see if this Analyzer is still needed. Please let me know if any of the above is incorrect and thank you for your help and explanation.

[CyrusNajmabadi]

Based on my reading, the advantage is in readability and to reduce the chance of a hidden zero width space character.

I personally think the readability is fine :-). The zwsp is interesting. But it hasn't ever been an issue for us, so I don't think it's really needed to change here.

[elachlan]

Agreed. I will suggest msbuild doesn't take on this analyzer. I might look at an analyzer for zwsp to highlight any usages to help detect issues.

Thank you for your help @CyrusNajmabadi it is much appreciated.