advanced patterns with Regex in C# When Matching Special Characters
I'm performance testing and I'm not sure how to approach I'm working with an scenario with a regex pattern in C# that doesn't seem to behave as expected when matching strings that contain special characters. I'm using the `System.Text.RegularExpressions.Regex` class in .NET 6.0. The pattern I have is supposed to match a string that starts with a letter followed by any number of alphanumeric characters or underscores. However, it's not matching strings that contain special characters like hyphens or periods as I thought it would. Here’s the regex pattern I’m using: ```csharp string pattern = "^[a-zA-Z][a-zA-Z0-9_]*$"; ``` I expected it to match the string "test-string_123" but it doesn’t. Instead, it only matches strings like "testString123" or "test_string". I've tried modifying the regex by adding `[-.]` to include hyphens and periods, but it seems to mess up the matching logic. Here's the updated pattern I tried: ```csharp string pattern = "^[a-zA-Z][-a-zA-Z0-9_.]*$"; ``` This leads to unexpected matches, and I don’t know if I’m handling the character classes correctly. The behavior I get when I test it on a string like "test-string_123" is that it returns `false`. I’m not sure if I’m misinterpreting the regex syntax or if there's an scenario with how I'm applying it in my code. To test, I'm using: ```csharp string input = "test-string_123"; bool isMatch = Regex.IsMatch(input, pattern); ``` I would appreciate any insights on how to properly construct this regex to meet my requirements without excluding valid input. What am I missing here? The stack includes C# and several other technologies. Any help would be greatly appreciated!