C# string comparison ignoring spaces, carriage return or line breaks

You should normalize each string by removing the characters that you don't want to compare and then you can perform a String.Equals with a StringComparison that ignores case.

Something like this:

string s1 = "HeLLo    wOrld!";
string s2 = "Hello\n    WORLd!";

string normalized1 = Regex.Replace(s1, @"\s", "");
string normalized2 = Regex.Replace(s2, @"\s", "");

bool stringEquals = String.Equals(
    normalized1, 
    normalized2, 
    StringComparison.OrdinalIgnoreCase);

Console.WriteLine(stringEquals);

Here Regex.Replace is used first to remove all whitespace characters. The special case of both strings being null is not treated here but you can easily handle that case before performing the string normalization.

This may also work.

String.Compare(s1, s2, CultureInfo.CurrentCulture, CompareOptions.IgnoreCase | CompareOptions.IgnoreSymbols) == 0

Edit:

IgnoreSymbols: Indicates that the string comparison must ignore symbols, such as white-space characters, punctuation, currency symbols, the percent sign, mathematical symbols, the ampersand, and so on.

Remove all the characters you don't want and then use the ToLower() method to ignore case.

edit: While the above works, it's better to use StringComparison.OrdinalIgnoreCase. Just pass it as the second argument to the Equals method.