Question

I’m having a little trouble figuring out how to call the Parallel.ForEach with a 2D array of strings:

string[,] board = new string[,]{
        {"A", "B", "C", "D", "E" },
        {"F", "G", "H", "I", "J"},
        {"K", "L", "M", "N", "O"},
        {"0", "1", "2", "3", "4"}};

Parallel.ForEach(board, row =>
    {
        for (int i = 0; i < row.Length; ++i)
        {
            // find all valid sequences
        }
    });

If I don’t specify the type explicitly I get the following error:

The type arguments for method
‘System.Threading.Tasks.Parallel.ForEach(System.Collections.Generic.IEnumerable,
System.Action)’ cannot be
inferred from the usage. Try
specifying the type arguments
explicitly.

What’s the proper way to specify the type arguments explicitly?

Answer 1

The problem for you is that 2-dimensional arrays do not implement IEnumerable<one-dimensional-array>. (It does implement IEnumerable, but it’s an IEnumerable of strings that “flattens” the array.) You can do two things:

• Change the string[,] to a jagged array-of-arrays, string[][].

• Implement your own extension method that iterates over a two-dimensional array and turns it into an IEnumerable<one-dimensional-array>.