diff --git a/Data/Repository/IUserRepository.cs b/Data/Repository/IUserRepository.cs
index e69de29..9560b00 100644
--- a/Data/Repository/IUserRepository.cs
+++ b/Data/Repository/IUserRepository.cs
@@ -0,0 +1,17 @@
+using Demo.domain.Models;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Demo.Data.Repository
+{
+    public interface IUserRepository
+    {
+        List<UserLocalEntity> GetAllUser();
+        bool RemoveUserByGuid(Guid userGuid);
+        UserLocalEntity? UpdateUser(UserLocalEntity userUpdateLocalEntity);
+        UserLocalEntity? GetUserByGuid(Guid userGuid);
+    }
+}
\ No newline at end of file
diff --git a/Demo.csproj b/Demo.csproj
index 6f10314..28a3ec0 100644
--- a/Demo.csproj
+++ b/Demo.csproj
@@ -11,4 +11,8 @@
     <Folder Include="Data\RemoteData\" />
   </ItemGroup>
 
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="8.0.1" />
+  </ItemGroup>
+
 </Project>
\ No newline at end of file
diff --git a/Domain/UseCase/GroupUseCase.cs b/Domain/UseCase/GroupUseCase.cs
index bc99c1f..dedaadc 100644
--- a/Domain/UseCase/GroupUseCase.cs
+++ b/Domain/UseCase/GroupUseCase.cs
@@ -8,17 +8,17 @@ using System.Threading.Tasks;
 
 namespace Demo.Domain.UseCase
 {
-    public class GroupUseCase
+    public class GroupUseCase:IGroupUseCase
     {
 
-        private GroupRepositoryImpl _repositoryGroupImpl;
+        private IGroupRepository _repositoryGroupImpl;
         
-        public GroupUseCase(GroupRepositoryImpl repositoryGroupImpl)
+        public GroupUseCase(IGroupRepository groupRepository)
         {
-            _repositoryGroupImpl = repositoryGroupImpl;
+            _repositoryGroupImpl = groupRepository;
         }
 
-        public List<Group> GetAllGroups() => _repositoryGroupImpl.GetAllGroups
+        public List<Group> GetAllGroups() => _repositoryGroupImpl.GetAllGroup()
             .Select(it => new Group { Id  = it.Id, Name = it.Name}).ToList();
 
         public Group UpdateGroupName(Group group) {
@@ -41,6 +41,11 @@ namespace Demo.Domain.UseCase
 
         }
 
+        public bool RemoveGroupById(int groupId) {
+
+            return _repositoryGroupImpl.RemoveGroupById(groupId);
+        }
+
         public bool CreateGroup(Group group) {
 
             GroupLocalEntity? groupLocalEntity = new GroupLocalEntity{Id = group.Id, Name = group.Name};
@@ -48,5 +53,12 @@ namespace Demo.Domain.UseCase
             if (groupLocalEntity != null) return false;
             return true;
         }
+
+        public Group GetGroupById(int groupId) {
+
+            GroupLocalEntity? groupLocalEntity = _repositoryGroupImpl.GetGroupById(groupId);
+            if (groupLocalEntity == null) throw new Exception("");
+            return new Group { Id = groupLocalEntity.Id, Name = groupLocalEntity.Name };
+        }
     }
 }
diff --git a/Domain/UseCase/IGroupUseCase.cs b/Domain/UseCase/IGroupUseCase.cs
new file mode 100644
index 0000000..bf53584
--- /dev/null
+++ b/Domain/UseCase/IGroupUseCase.cs
@@ -0,0 +1,18 @@
+using Demo.domain.Models;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Demo.Domain.UseCase
+{
+    public interface IGroupUseCase
+    {
+        List<Group> GetAllGroups();
+        bool RemoveGroupById(int groupID);
+        Group UpdateGroupName(Group group);
+        Group GetGroupById(int groupID);
+        bool CreateGroup(Group group);
+    }
+}
\ No newline at end of file
diff --git a/Domain/UseCase/IUserUseCase.cs b/Domain/UseCase/IUserUseCase.cs
new file mode 100644
index 0000000..6dd57e1
--- /dev/null
+++ b/Domain/UseCase/IUserUseCase.cs
@@ -0,0 +1,18 @@
+using Demo.domain.Models;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Demo.Domain.UseCase
+{
+    public interface IUserUseCase
+    {
+        List<Group> GetAllGroups();
+        List<User> GetAllUsers();
+        User GetUserByGuid(Guid userGuid);
+        bool RemoveUserByGuid(Guid userGuid);
+        User UpdateUser(User user);
+    }
+}
\ No newline at end of file
diff --git a/Domain/UseCase/UserUseCase.cs b/Domain/UseCase/UserUseCase.cs
index 89b23b7..91591cc 100644
--- a/Domain/UseCase/UserUseCase.cs
+++ b/Domain/UseCase/UserUseCase.cs
@@ -8,21 +8,21 @@ using System.Threading.Tasks;
 
 namespace Demo.Domain.UseCase
 {
-    public class UserUseCase
+    public class UserUseCase:IUserUseCase
     {
-        private  readonly UserRepositoryImpl _repositoryUserImpl;
-        private  readonly GroupRepositoryImpl _repositoryGroupImpl;
+        private  readonly IUserRepository _repositoryUserImpl;
+        private  readonly IGroupRepository _repositoryGroupImpl;
 
-        public UserUseCase(UserRepositoryImpl repositoryImpl, GroupRepositoryImpl repositoryGroupImpl)
+        public UserUseCase(IUserRepository userRepository, IGroupRepository groupRepository)
         {
-            _repositoryUserImpl = repositoryImpl;
-            _repositoryGroupImpl = repositoryGroupImpl;
+            _repositoryUserImpl = userRepository;
+            _repositoryGroupImpl = groupRepository;
         }
 
-        private List<Group> GetAllGroups() => _repositoryGroupImpl.GetAllGroups
+        public List<Group> GetAllGroups() => _repositoryGroupImpl.GetAllGroup()
             .Select(it => new Group { Id  = it.Id, Name = it.Name}).ToList();
-        public List<User> GetAllUsers() => _repositoryUserImpl.GetAllUsers
-            .Join(_repositoryGroupImpl.GetAllGroups,
+        public List<User> GetAllUsers() => _repositoryUserImpl.GetAllUser()
+            .Join(_repositoryGroupImpl.GetAllGroup(),
             user => user.GroupID,
             group => group.Id,
             (user, group) => 
diff --git a/Program.cs b/Program.cs
index 4bcac7c..a97ffea 100644
--- a/Program.cs
+++ b/Program.cs
@@ -2,10 +2,19 @@
 using Demo.Data.Repository;
 using Demo.Domain.UseCase;
 using Demo.UI;
+using Microsoft.Extensions.DependencyInjection;
 
-GroupRepositoryImpl groupRepositoryImpl = new GroupRepositoryImpl();
-UserRepositoryImpl userRepositoryImpl = new UserRepositoryImpl();
-UserUseCase userUseCase = new UserUseCase(userRepositoryImpl, groupRepositoryImpl);
-GroupUseCase groupUseCase = new GroupUseCase(groupRepositoryImpl);
+IServiceCollection services = new ServiceCollection();
 
-MainMenuUI mainMenuUI = new MainMenuUI(userUseCase, groupUseCase);
+services
+    .AddSingleton<IGroupRepository, GroupRepositoryImpl>()
+    .AddSingleton<IUserRepository, UserRepositoryImpl>()
+    .AddSingleton<IGroupUseCase, GroupUseCase>()
+    .AddSingleton<IUserUseCase, UserUseCase>()
+    .AddSingleton<UserConsoleUI>()
+    .AddSingleton<GroupConsoleUI>()
+    .AddSingleton<MainMenuUI>();
+
+var serviceProvider = services.BuildServiceProvider();
+
+MainMenuUI mainMenuUI = serviceProvider.GetService<MainMenuUI>();
diff --git a/UI/GroupConsole.cs b/UI/GroupConsole.cs
index bb2cf12..3d4bafd 100644
--- a/UI/GroupConsole.cs
+++ b/UI/GroupConsole.cs
@@ -7,9 +7,9 @@ namespace Demo.UI
 {
     public class GroupConsoleUI 
     {
-        GroupUseCase _groupUseCase;
+        IGroupUseCase _groupUseCase;
 
-        public GroupConsoleUI(GroupUseCase groupUseCase) {
+        public GroupConsoleUI(IGroupUseCase groupUseCase) {
             _groupUseCase = groupUseCase; 
         }
 
diff --git a/UI/MainMenu.cs b/UI/MainMenu.cs
index 16e9982..a1543d1 100644
--- a/UI/MainMenu.cs
+++ b/UI/MainMenu.cs
@@ -14,7 +14,7 @@ namespace Demo.UI
         UserConsoleUI _userConsoleUI;
         GroupConsoleUI _groupConsoleUI;
 
-        public MainMenuUI(UserUseCase userUseCase, GroupUseCase groupUseCase) { 
+        public MainMenuUI(IUserUseCase userUseCase, IGroupUseCase groupUseCase) { 
         _userConsoleUI = new UserConsoleUI(userUseCase);
         _groupConsoleUI = new GroupConsoleUI(groupUseCase);
             DisplayMenu();
diff --git a/UI/UserConsole.cs b/UI/UserConsole.cs
index 43dc3df..e895507 100644
--- a/UI/UserConsole.cs
+++ b/UI/UserConsole.cs
@@ -10,8 +10,8 @@ namespace Demo.UI
 {
     public class UserConsoleUI
     {
-        UserUseCase _userUseCase;
-        public UserConsoleUI(UserUseCase userUseCase) {
+        IUserUseCase _userUseCase;
+        public UserConsoleUI(IUserUseCase userUseCase) {
             _userUseCase = userUseCase;
         }