サービス定義

SearchService.cs

using System.ServiceModel;

namespace Hoge
{
    [ServiceContract]
    public interface ISearchService
    {
        [OperationContract]
        void Execute();
    }

    [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple, UseSynchronizationContext = false)]
    public class SearchService : ISearchService
    {
        public delegate void Searcher();

        public Searcher SercherDelegate;

        public void Execute()
        {
            SercherDelegate();    // 実装はデリゲートします
        }
    }
}

サービス起動

SearchService service = new SearchService();
service.SercherDelegate = hogeForm.SearchRequest;    // デリゲート登録

serviceHost = new ServiceHost(
    service,
    new Uri("net.pipe://localhost/Hoge"));

try
{
    serviceHost.AddServiceEndpoint(
        typeof(ISearchService),
        new NetNamedPipeBinding(),
        "SearchService");
    serviceHost.Open();
}
catch (AddressAlreadyInUseException)
{
    MessageBox.Show("既にサービスは起動しています。");
}
catch (Exception e)
{
    MessageBox.Show(e.ToString());
}

サービス呼び出し（クライアント）

new ChannelFactory<ISearchService>(
    new NetNamedPipeBinding(),
    new EndpointAddress("net.pipe://localhost/Hoge/SearchService")).CreateChannel()
    .Execute();