Declaring a Dictionary> with Functions already inside them c#

Question

First of all, I don't even know what to use when passing on 4 parameters but no return value, I'll just use Func as an example.

I do not want to use Dictionary.Add to insert my function, I want it to be inside while initializing the dictionary.

Dictionary<string, Func<int, int, int, int>> types = new Dictionary<string, 
{"Linear", Func<int, int, int, int>> //idk how to write this part
{ 
    code here
}}

Have you read the [documentation](https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/how-to-initialize-a-dictionary-with-a-collection-initializer)? — BJ Myers, Oct 01 '17 at 16:11
Did you forget to write the method that can be called through this dictionary? That is what is missing, its name. — Hans Passant, Oct 01 '17 at 16:14

stelioslogothetis · Answer 1 · 2017-10-01T16:15:06.497

For a Func like the one you have in your question, this should work:

var myDict = new Dictionary<string, Func<int, int, int, int>>()
{
    {"Linear", (int a, int b, int c) => { return 0; } }
};

Note that you always need to have a return in your function.

If you want something that does not have a return value, you shouldn't use a Func, but an Action instead:

var myDict = new Dictionary<string, Action<int, int, int, int>>()
{
    {"Linear", (int a, int b, int c, int d) => { } }
};

Unlike functions, actions do not return anything.

Note the difference in meaning between Action<int, int, int, int> and Func<int, int, int, int>. In the former, the last int indicates the type of the 4th parameter, whereas in the latter it indicates the return type.

Declaring a Dictionary> with Functions already inside them c#

1 Answers1