The following code will always return -1.
"Example\\̼".IndexOf("Example\\");
This is because the Combining Seagull Below character, U+033C, is a combining character, and it will combine with the character previous to it in order to produce a new character. Using an ordinal string comparison would fix this problem for you. As an example, the following code will always return 0:
"Example\\̼".IndexOf("Example\\", StringComparison.OrdinalIgnoreCase)
The following code will always, also return -1.
"µ".IndexOf("μ");
This is because, although µ and μ are the same symbol, they are actually two different characters that are part of the Unicode character set (one is called the Micro Sign character, U+00B5, and the other is the Greek Small Letter Mu character, U+03BC). Using an ordinal string comparison will not fix this, but normalization will. The following code will always return 0:
"µ".Normalize(NormalizationForm.FormKD).IndexOf("μ".Normalize(NormalizationForm.FormKD))
