Exception or Either monad in C#

Question

I am trying to grok get a preliminary understanding of monads.

I have a data layer call whose result I would like to return monadically either as a result e

Answer 1

We have implemented Either data structure in our C# solution and we are happy using it. Here is the most simple version of such implementation:

public class Either
{
    private readonly TL left;
    private readonly TR right;
    private readonly bool isLeft;

    public Either(TL left)
    {
        this.left = left;
        this.isLeft = true;
    }

    public Either(TR right)
    {
        this.right = right;
        this.isLeft = false;
    }

    public T Match(Func leftFunc, Func rightFunc)
        => this.isLeft ? leftFunc(this.left) : rightFunc(this.right);

    public static implicit operator Either(TL left) => new Either(left);

    public static implicit operator Either(TR right) => new Either(right);
}

(our code has more helper methods, but they are optional)

The main points are

• You are only able to set Left or Right
• There are implicit operators to make instantiation easier
• There is a Match method for pattern matching

I've also described how we use this Either type for data validation.