Ez is itt félig kész ...

src/WorkFlowCheck.BL/Services/CheckListService.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace WorkFlowCheck.BL.Services
+{
+    class CheckListService
+    {
+    }
+}

src/WorkFlowCheck.BL/Services/Interfaces/ICheckListService.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using WorkFlowCheck.Common.DTO;
+
+namespace WorkFlowCheck.BL.Services.Interfaces
+{
+    public interface ICheckListService
+    {
+        Task<CheckListHeaderDTO> GetCheckListHeader(int Id);
+    }
+}