Regex Not Matching Custom Alphanumeric IDs with Specific Lengths in C# - Handling Edge Cases
I've searched everywhere and can't find a clear answer. I'm trying to validate a set of custom alphanumeric IDs in C# that must be exactly 8 characters long, consisting of 4 uppercase letters followed by 4 digits, for example, `ABCD1234`. However, my regex pattern seems to be failing in certain scenarios, specifically with edge cases where the IDs might inadvertently include special characters or be of incorrect lengths. Here’s the regex pattern I’m currently using: ```csharp string pattern = "^[A-Z]{4}\d{4}$"; ``` I'm using `Regex.IsMatch` to validate the IDs. The question arises when I test it with inputs like `ABCD@1234` or `ABCD123`, which should return false but sometimes it behaves unexpectedly due to whitespace or other non-visible characters in the string. To troubleshoot, I tried trimming the input and using `RegexOptions.IgnorePatternWhitespace`, but the results are still inconsistent. Here’s a snippet of my validation method: ```csharp public bool IsValidId(string id) { id = id.Trim(); // Attempted to handle whitespace return Regex.IsMatch(id, pattern); } ``` When I run the validation on inputs like ` ABCD1234 ` (with leading/trailing spaces), it fails to return `false` as expected. I also get unexpected results with `ABCD123@`, which should definitely not match. What am I missing here? Is there a better approach to ensure that the ID strictly adheres to the required format without being thrown off by special characters or whitespace? Any suggestions for refining my regex or handling inputs would be greatly appreciated! This is part of a larger API I'm building.