public interface IOptionsMonitorCustom<out TOptions> : Microsoft.Extensions.Options.IOptionsMonitor<TOptions>

    where TOptions  :   class

{ }

​

public class OptionsMonitorCustom<TOptions> : Microsoft.Extensions.Options.OptionsMonitor<TOptions>, IOptionsMonitorCustom<TOptions>

    where TOptions  :   class

{ 

    public OptionsMonitorCustom(

        [

            System.Diagnostics.CodeAnalysis.AllowNull

        ] Microsoft.Extensions.Options.IOptionsFactory<

            TOptions

        > factory = default,

        [

            System.Diagnostics.CodeAnalysis.AllowNull

        ] System.Collections.Generic.IEnumerable<

            Microsoft.Extensions.Options.IOptionsChangeTokenSource<

                TOptions

            >

        > changeTokens = default, 

        [

            System.Diagnostics.CodeAnalysis.AllowNull

        ] Microsoft.Extensions.Options.IOptionsMonitorCache<

            TOptions

        > cache = default

    ) : base(

        factory         ?? GetOptionsMonitorFactory( ),

        changeTokens    ?? GetOptionsChangeTokenSources( ),

        cache           ?? GetOptionsCache( )

    )

    { }

    public static Microsoft.Extensions.Options.IOptionsFactory<

        TOptions

    > GetOptionsMonitorFactory( )

    {

        System.Collections.Generic.List<

            Microsoft.Extensions.Options.ConfigureOptions<

                TOptions

            >

        > setups = new ( ) { };

        System.Collections.Generic.List<

            Microsoft.Extensions.Options.PostConfigureOptions<

             TOptions

            >

        > postConfigures = new ( ) { };

​

        Microsoft.Extensions.Options.OptionsFactory<

            TOptions

        > factory =

            new (

                setups:         setups,

                postConfigures: postConfigures 

            ) { };

        return factory;

    }

​

    public static System.Collections.Generic.List<

        Microsoft.Extensions.Options.IOptionsChangeTokenSource<

            TOptions

        >

    > GetOptionsChangeTokenSources( )

    {

        System.Collections.Generic.List<

            Microsoft.Extensions.Options.IOptionsChangeTokenSource<

                TOptions

            >

        > sources = new ( ) { };

        return sources;

    }

    public static Microsoft.Extensions.Options.OptionsCache<

        TOptions

    > GetOptionsCache( )

    {

        Microsoft.Extensions.Options.OptionsCache<

            TOptions

        > cache = new ( ) { };

        return cache;

    }

}

​

public class Program

{

    public static void Main( )

    {

        IOptionsMonitorCustom<object> objectOptionsMonitor = new OptionsMonitorCustom<object>( ) { };

​

        IOptionsMonitorCustom<string> stringOptionsMonitor = new OptionsMonitorCustom<string>( ) { };

​

        System.Console.WriteLine("Before OptionsMonitor implicit casting via Covariance.\r\n");

​

        objectOptionsMonitor = stringOptionsMonitor;

​

        System.Console.WriteLine("After OptionsMonitor implicit casting via Covariance.\r\n");

    }

}

​