C# Maybe Monad as Linq

MaybeLinq.cs

using System;
using System.Collections.Generic;
using System.Linq;


public abstract class Maybe<T> {
    
    public Maybe<TResult> Map<TResult>(Func<T, TResult> selector)
    {
        return this.Bind(a => new Just<TResult>(selector(a)));
    }
    
    public Maybe<TResult> Select<TResult>(Func<T, TResult> selector)
    {
        return this.Map(selector);
    }
    

    public abstract Maybe<TResult> Bind<TResult>(Func<T, Maybe<TResult>> tempSelector);

    
    public Maybe<TResult> SelectMany<TTemp, TResult>(Func<T, Maybe<TTemp>> tempSelector, Func<T, TTemp, TResult> resultSelector)
    {
        return this.Bind(a => tempSelector(a).Map(b => resultSelector(a, b)));
    }
}


public class Nothing<T> : Maybe<T> {
    public override string ToString()
    {
        return "Nothing";
    }
    
    public override Maybe<TResult> Bind<TResult>(Func<T, Maybe<TResult>> tempSelector)
    {
        return new Nothing<TResult>();
    }
}

public class Just<T> : Maybe<T> {
    public Just(T t) {
        this.Value = t;
        
    }
    
    public T Value { set; get;}
    
    public override string ToString()
    {
        return $"Just {this.Value}";
    }
    
    public override Maybe<TResult> Bind<TResult>(Func<T, Maybe<TResult>> tempSelector)
    {
        return tempSelector(this.Value);
    }
    
}

public class Hello{
    public static void Main(){
        // Your code here!
        
        var query1 =
            from x in new Just<int>(1)
            from y in new Just<int>(2)
            select x + y;

        var query2 =
            from x in new Just<int>(1)
            from y in new Nothing<int>()
            select x + y;
        

        var query3 =
            from x in new Nothing<int>()
            from y in new Just<int>(2)
            select x + y;
        
        var query4 =
            from x in new Nothing<int>()
            from y in new Nothing<int>()
            select x + y;

        var query5 =
            from x in new Just<int>(1)
            from y in new Just<int>(2)
            from z in new Just<int>(3)
            select x + y + z;
        
        var query6 =
            from x in new Just<int>(1)
            from y in new Nothing<int>()
            from z in new Just<int>(3)
            select x + y + z;
        
        var qs = new List<Maybe<int>>{
            query1,
            query2,
            query3,
            query4,
            query5,
            query6,
        };

        qs.ForEach(System.Console.WriteLine);

    }
}

TODO: Select, SelectMany as Extension Methods.