Why doesn't this regex pattern match this text? (Simple regex just includes escaped text with wildcard in the middle)

Question

Apologies if this is a duplicate; I promise I did search.

I'm working on a C# integration testing project using NUnit in Visual Studio 2010 Professional, running the tests with Resharper v6.1. (Resharper 6.1 dictates that I use NUnit 2.5.10; I've always had trouble trying to override that.)

Part of my testing is to assert that the proper exceptions are thrown, including the exception messages. However, sometimes the exception message includes a guid or other information that I don't expect to be the exact same every time. To get around this, I want to match the exception message using a basic regex pattern where I include the exception message and simply use a wildcard where in certain spots to say "this part can match anything" I've tried to do this in the scenario below, but every time I get an error that there is no match. Summary of the code:

[Test]
public void ExceptionPatternTest()
{
var patternA = Regex.Escape(@"SQL Code: 2601 Message: Cannot insert duplicate key row in object 'dbo.ResourceCategory' with unique index 'IDX_ResourceTypeResourceCategoryName'.");
var patternB = ".*";  //wildcard
var patternC = Regex.Escape(@"\r\nThe statement has been terminated.");    
var pattern = patternA + patternB + patternC;

var thrownException = Assert.Throws(Is.TypeOf(_testException.GetType()),
               () => Throw()); //Call method and assert that exception is thrown.

Assert.That(Regex.IsMatch(thrownException.Message, pattern));
}

private void Throw()
{
    throw _testException;
}

readonly Exception _testException = new Exception("SQL Code: 2601 Message: Cannot insert duplicate key row in object 'dbo.ResourceCategory' with unique index 'IDX_ResourceTypeResourceCategoryName'. The duplicate key value is (9fec90c1-12b4-42c3-adc0-a0d600b9a8e8, 1, Item Cat 1).\r\nThe statement has been terminated.");

I've also tried variations on parts of this. Including a manual escaping of characters for the pattern:

var pattern = @"SQL\ Code:\ 2601\ Message:\ Cannot\ insert\ duplicate\ key\ row\ in\ object\ 'dbo\.ResourceCategory'\ with\ unique\ index\ 'IDX_ResourceTypeResourceCategoryName'\..*\\r\\nThe\ statement\ has\ been\ terminated\.";

And I've tried StringAssert too, in case there was a difference:

StringAssert.IsMatch(pattern, thrownException.Message);

Thanks in advance for your help! Also, apologies if I'm just missing something really dumb. I've only worked with regex sparingly, so that is certainly possible.

Answer 1

Regex.Escape(@"\r\n") will produce \\r\\n, which is not what you want. I would suggest moving the newline to the unescaped string instead:

var patternB = @".*\r\n";
var patternC = Regex.Escape(@"The statement has been terminated.");    

Answer 2

Why use a complicated regex when you can just use string.StartsWith and string.EndsWith to check the prefix and suffix? Less code, easier to read, and no messing about trying to work out why a seemingly simple thing doesn't work right.