good job

Fixed with a generalized description

Because the prefix need to be ignored, read again the last paragraph.

I don't understand why the correct answer is “true” in the test case "normalString3"

IEnumerable<string> columns = new string[] { "1:Good Morning.", "Good Morning." };
Assert.AreEqual(true, instance.testCompare(columns, 7));

I just learned that c# has arrow syntax. Cheers!!

me either

Fixed

I did the other way, because I liked how it looked.

But yours surely looks way, waaay better. Well done fella!

I did the same, almost rsrs

Please try to use the common sense a grade schooler would use to evaluate this question.

I believe a grade schooler will instead yell at the teacher "what the fuck are you doing" if the teacher decides to do this.

This is an insult to what a teacher and student is. Teacher is supposed to do their job explaining things in a way that students can actually understand. Please don't abuse your students and claim you have the authority to do so.

Re-raising the issue below:

Why using IEnumerable<string> when you always pass a length 2 array?

Notably, this implementation goes against C# conventions (specifically the IComparer interface) and hence is completely useless for any actual use.

This is not an acceptable answer, so re-raising the issue.

Inputs are not strings anymore.