Greater Than and Less Than Symbols in C# Regular Expression

Question

I am using a Regex pattern "MilliSeconds\\s\\<" and try to compare with the input "MilliSeconds <" but everytime my Regex match is getting failed. Can anyone tell what is wrong here?

MilliSeconds followed by backslash and <

string value = @"MilliSecs <Test Run";
string pattern = @"MilliSecs\s\&lt;";

Match mtchObj = Regex.Match(value,pattern);

if(mtchObj.Success)
{
    MessageBox.Show("Matched");
}

Which my input string is not getting matched with the pattern?

Answer 1

Note that the regex engine does not know of XML escaped strings, and < does not stand both for a < string and < character. In other words, these entities are not identical for the regex engine.

It appears you can modify the pattern . Note that it is possible to match either < or < with the help of alternation and grouping :

@"MilliSeconds\s(?:&lt;|<)"
                ^^^^^^^^^^

So, (?:&lt;|<) is a non-capturing group that tries to match < and if it is not found, < is tried.

Answer 2

Use simply string pattern = @"MilliSecs\\s<"; , there is no need to escape < in this regex since it doesn't have a special meaning. You code should be:

string value = @"MilliSecs <Test Run";
string pattern = @"MilliSecs\s<";

Match mtchObj = Regex.Match(value,pattern);

if(mtchObj.Success)
{
    MessageBox.Show("Matched");
}