Regular expressions question

hi!
Is it somehow possible to get use the regex "test*blah" and filter what's * out from the text?

Code:

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                        Regex regex = new Regex("test*blah");
                        Match match = regex.Match("YYYtestXXXblahZZZ");
                        if (match.Value == "XXX") MessageBox.Show("That's what I want!!!");

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i suppose it must look like this, but i don't quite get what i want...

thanks in advance :)

"Normally" you would use a regex like "test(.*)blah" and then use the backreference \1 to refer to the first parenthesized sub-expression (which in this case would appear to be what you want). The C# syntax for backreferences looks a little weird; if I'm reading it right, it would be something like

Code:

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"test(?<1>.*)blah"

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and then

Code:

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"${1}"

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in your Result would be what you want. (Of course, with this syntax you can give the thing a meaningful name, instead of "1".)

Here's the exact code you should need, including a named parameter:

Code:

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// ExplicitCapture isn't strictly necessary, it makes sure no unnamed groups are captured. 
// If you only use named groups, turning ExplicitCapture on will improve speed and reduce memory usage.
Regex ex = new Regex(@"test(?'YourNamedParameter'.*)blah", RegexOptions.ExplicitCapture);

// This also works:
// Regex ex = new Regex(@"test(?<YourNamedParameter>.*)blah", RegexOptions.ExplicitCapture);

string input = "YYYtestXXXblahZZZ"

Match m = ex.Match(input);
if (m != null)
{
    string value = m.Groups["YourNamedParameter"].Value;
}

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Here's a tutorial on how to make and use regular expressions, this is practically a regex bible:
Regular Expression Tutorial - Learn How to Use Regular Expressions

works like a charm. thanks for the quick reply :)

wait a minute: what's with this:
"testXXXblahYYYblah"

i should get: "XXX"
but i get "XXXblahYYY"

???

Quote:

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Originally Posted by Devils Child

wait a minute: what's with this:
"testXXXblahYYYblah"

i should get: "XXX"
but i get "XXXblahYYY"

???

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Because that's what matches. Regex is greedy, and will always take the largest substring that fits the pattern.

Quote:

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Originally Posted by tabstop

Because that's what matches. Regex is greedy, and will always take the largest substring that fits the pattern.

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That's also covered in that regex tutorial I linked (in the chapter on repetition), but the non-greedy way would be to do this:

@"test(?'YourNamedParameter'.*?)blah"

works! thanks a lot :)