using System;

using System.Collections.Generic;

​

public interface ISearchOptions

{

    string Name { get; }

}

​

public class FooSearchOptions  : ISearchOptions

{

    public string Name => "aaa";

}

​

public class BaaSearchOptions  : ISearchOptions

{

    public string Name => "bbb";

}

​

​

​

// Common interface.

public interface ISearchService<in TSearchOptions> where TSearchOptions : ISearchOptions

{

}

​

// Concrete #1.

public class FooSearchService : ISearchService<FooSearchOptions>

{

}

​

// Concrete #2.

public class BaaSearchService : ISearchService<BaaSearchOptions>

{

}

​

​

​

​

public class Program

{

    public static void Main()

    {

        var searchServices = new List<ISearchService<ISearchOptions>>

        {

            new FooSearchService(),

            new BaaSearchService()

        };

    }

}