using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var compositeFilter = GetLetterFilter().And(GetLengthFilter(), GetSpaceFilter());

        var source = new[]{"", "Alabama", "", "Wachinton DC"};

        var matches = source.AsEnumerable().Where(compositeFilter);

        Console.WriteLine(string.Join(", ", matches));

    }

    public static Func<string, bool> GetLetterFilter()

    {

        return x => x.Contains("a");

    }

    public static Func<string, bool> GetLengthFilter()

    {

        return x => x.Length > 5;

    }

    public static Func<string, bool> GetSpaceFilter()

    {

        return x => x.Contains(" ");

    }   

}

​

public static class FuncExtensions

{

    public static Func<T, bool> And<T>(this Func<T, bool> arg0, Func<T, bool> arg1)

    {

        return x => arg0(x) && arg1(x);

    }

    public static Func<T, bool> And<T>(this Func<T, bool> arg0, Func<T, bool> arg1, Func<T, bool> arg2)

    {

        return x => arg0(x) && arg1(x) && arg2(x);

    }

​

    public static Func<T, bool> And<T>(this Func<T, bool> arg0, Func<T, bool> arg1, Func<T, bool> arg2, Func<T, bool> arg3)

    {

        return x => arg0(x) && arg1(x) && arg2(x) && arg3(x);

    }

}