using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    private Switch<int, Action> _simpleSwitch;

    private Switch<int, Action> _complexSwitch;

    public void Main()

    {

        Console.WriteLine("**** Simple Cases");

        TestSimpleCases();

        Console.WriteLine("\n\n**** Complex Cases");

        TestComplexCases();

    }

    private void TestSimpleCases()

    {

        _simpleSwitch = new Switch<int, Action>(GetSimpleCases(), () => Console.WriteLine("Does not equal 3, 30, or 300"));

        PrintSimpleGetValue(3);

        PrintSimpleGetValue(30);

        PrintSimpleGetValue(300);

        PrintSimpleGetValue(301);

        PrintSimpleGetValue(500);

        Console.WriteLine("Inserting 500 as case");

        // Add 500

        _simpleSwitch.AddCase(500, () => Console.WriteLine("Equals 500"));

        _simpleSwitch.UpdateDefault(() => Console.WriteLine("Does not equal 3, 30, 300, or 500"));

        PrintSimpleGetValue(500);

    }

    private void TestComplexCases()

    {

        _complexSwitch = new Switch<int, Action>(GetComplexCases(), () => Console.WriteLine("Number not in any case range"));

        PrintComplexGetValue(3);

        PrintComplexGetValue(30);

        PrintComplexGetValue(300);

        PrintComplexGetValue(301);

        PrintComplexGetValue(500);

        Console.WriteLine("Inserting >=500 as case");

        // Add >500

        _complexSwitch.AddCase(x => x >= 500, () => Console.WriteLine("Greater than or equal to 500"));

        PrintComplexGetValue(500);

    }

    private void PrintSimpleGetValue(int number)

    {

        Console.Write(number + ": ");

        _simpleSwitch.GetValue(number)();

    }

    private void PrintComplexGetValue(int number)

    {

        Console.Write(number + ": ");

        _complexSwitch.GetValue(number)();

    }

    private Dictionary<int, Action> GetSimpleCases()

    {

        return new Dictionary<int, Action>

        {

            { 3, () => Console.WriteLine("Equals 3") },

            { 30, () => Console.WriteLine("Equals 30") },

            { 300, () => Console.WriteLine("Equals 300") }

        };

    }

    private Dictionary<Predicate<int>, Action> GetComplexCases()

    {

        return new Dictionary<Predicate<int>, Action>

        {

            { x => x <= 3, () => Console.WriteLine("Smaller than or equal to 3") },

            { x => x <= 30, () => Console.WriteLine("Smaller than or equal to 30") },

            { x => x <= 300, () => Console.WriteLine("Smaller than or equal to 300") }

        };

    }

}

​

public class Switch<TKey, TValue>

{

    readonly Dictionary<Predicate<TKey>, TValue> Cases;

    TValue Default;

    public Switch(TValue @default)

    {

        Default = @default;

        this.Cases = new Dictionary<Predicate<TKey>, TValue>();

    }

    public Switch(Dictionary<TKey, TValue> cases, TValue @default) : this(@default)

    {

        cases.ToList().ForEach(kvp => AddCase(kvp.Key, kvp.Value));

    }

    public Switch(Dictionary<Predicate<TKey>, TValue> cases, TValue @default) : this(@default)

    {

        cases.ToList().ForEach(kvp => AddCase(kvp.Key, kvp.Value));

    }

    public TValue GetValue(TKey @case)

    {       

        var caseValue = Cases.FirstOrDefault(kvp => kvp.Key(@case));        

        if (!caseValue.Equals(default(KeyValuePair<Predicate<TKey>, TValue>)))

            return caseValue.Value;

        return this.Default;

    }

    public void AddCase(TKey @case, TValue value)

    {

        AddCase(t => t.Equals(@case), value);

    }

    public void AddCase(Predicate<TKey> @case, TValue value)

    {

        Cases[@case] = value;

    }

    public void UpdateDefault(TValue @default)

    {

        this.Default = @default;

    }

}