Simple string.Split failing with StringSplitOptions.TrimEntries

Question

This returns an array with only one element and thus throws an exception. But it works when I omit StringSplitOptions.TrimEntries.

using System;
                    
public class Program
{
    public static void Main()
    {
        Console.WriteLine("a-b".Split('+', '-', StringSplitOptions.TrimEntries)[1]);
    }
}

Could it be that it is picking this overload:

public string[] Split(char separator, int count, StringSplitOptions options = StringSplitOptions.None)

But since when in C# is char compatible with int?

Answer 1

since when in c# char is compatible with int?

char has been implicitly convertible to int in C# since version 1.

Could it be that it is picking this overload: ...

It has to be; it is the only overload that fits the method call. If this overload didn't exist, the code wouldn't compile.

I presume you expected this overload instead:

public string[] Split (char[]? separator, StringSplitOptions options)

However, this option is not compatible with the provided arguments, because the params modifier is not included as part of the signature (params must come last in the argument list). Therefore the '+', '-' portion of the method call cannot be interpreted as an array here. Nor is there an overload using IEnumerable<char> that could be chosen.

If you wish to use this other overload, you must ensure the array is fully-constructed before the method call resolves.