Linq error: “string[] does not contain a definition for 'Except'.”

Question

Here's my code:

    public static string[] SplitKeepSeparators(this string source, char[] keptSeparators, char[] disposableSeparators = null)
    {
        if (disposableSeparators == null)
        {
            disposableSeparators = new char[] { };
        }

        string separatorsString = string.Join("", keptSeparators.Concat(disposableSeparators));
        string[] substrings = Regex.Split(source, @"(?<=[" + separatorsString + "])");

        return substrings.Except(disposableSeparators); // error here
    }

I get the compile time error string[] does not contain a definition for 'Except' and the best extension method overload ... has some invalid arguments .

I have included using System.Linq in the top of the source file.

What is wrong?

Answer 1

Your substrings variable is a string[] , but disposableSeparators is a char[] - and Except works on two sequences of the same type.

Either change disposableSeparators to a string[] , or use something like:

return substrings.Except(disposableSeparators.Select(x => x.ToString())
                 .ToArray();

Note the call to ToArray() - Except just returns an IEnumerable<T> , whereas your method is declared to return a string[] .

Answer 2

Your problem is that you are using .Except<T>(this IEnumerable<T> source, IEnumerable<T> other) with two different types for T ( string and char ). Change your delimiters to a string array if you want to use Except.

https://msdn.microsoft.com/en-us/library/vstudio/bb300779%28v=vs.100%29.aspx