Question

I am trying to obtain the value part of this syntax:

[name:value]

I got as far as:

\[name:(\w*)]

Which matches the entire thing. Does anyone know the changes I would need to make to select only value? (Bearing in mind that syntax will also be surrounded by other text.

Answer 1

The Match.Result method is what you want. See API documentation and documentation on Regex substitution patterns.

Use Regex.Match(input, pattern).Result("$1") to get what you want.

To give a complete example, here is the unit test I used to confirm that this solution would work:

[Test]
public void TestRegexMatchResult() {
    var input = "Other text [name:value] and other text";
    var pattern = @"\[name:(\w+)\]";

    Assert.AreEqual("value", Regex.Match(input, pattern).Result("$1"));
}

The test passes.

You can also go through a string and extract multiple occurrences of the pattern:

[Test]
public void TestRegexMatchesResult() {
    var input = "Some [name:value] pairs [name:something] here.";
    var pattern = @"\[name:(\w+)\]";

    var results = Regex.Matches(input, pattern).OfType<Match>()
        .Select(match => match.Result("$1"));

    Assert.AreEqual(2, results.Count());

    Assert.AreEqual("value", results.ElementAt(0));
    Assert.AreEqual("something", results.ElementAt(1));
}

Finally, if you need to abstract this to something other than “name”, you can do this:

[Test]
public void TestMatchingNameAndValue() {
    var input = "[key:value] [another_key:some_other_value]";
    var pattern = @"\[(\w+):(\w+)\]";

    var results = Regex.Matches(input, pattern).OfType<Match>()
        .Select(match => new KeyValuePair<string, string>(
            match.Result("$1"),
            match.Result("$2")));

    Assert.AreEqual(2, results.Count());

    Assert.AreEqual("key", results.ElementAt(0).Key);
    Assert.AreEqual("value", results.ElementAt(0).Value);
    Assert.AreEqual("another_key", results.ElementAt(1).Key);
    Assert.AreEqual("some_other_value", results.ElementAt(1).Value);
}