diff --git a/WebApi/ManagerInterfaces/IAdministratorManager.cs b/WebApi/ManagerInterfaces/IAdministratorManager.cs
index b765df5..e1ff970 100644
--- a/WebApi/ManagerInterfaces/IAdministratorManager.cs
+++ b/WebApi/ManagerInterfaces/IAdministratorManager.cs
@@ -55,7 +55,7 @@ namespace ManagerInterfaces
         /// does not exist (<=> (nb-1)*count outside
         /// boundaries (0, getNbElement()-1)))
         /// </returns>
-        public Task<(int nbPages, ReadOnlyCollection<T>? administrators)> getAdministrators(int nb, int count, AdministratorOrderCriteria orderCriteria = AdministratorOrderCriteria.ById);
+        public Task<(int nbPages, IEnumerable<T>? administrators)> getAdministrators(int nb, int count, AdministratorOrderCriteria orderCriteria = AdministratorOrderCriteria.ById);
         /// <summary>
         /// get an administrator by his username
         /// </summary>
diff --git a/WebApi/ManagerInterfaces/IAnswerManager.cs b/WebApi/ManagerInterfaces/IAnswerManager.cs
index f1630fc..09acebe 100644
--- a/WebApi/ManagerInterfaces/IAnswerManager.cs
+++ b/WebApi/ManagerInterfaces/IAnswerManager.cs
@@ -28,7 +28,7 @@ namespace ManagerInterfaces
         /// does not exist (<=> (nb-1)*count outside
         /// boundaries (0, getNbElement()-1)))
         /// </returns>
-        public Task<(int nbPages, ReadOnlyCollection<T>? answers)> getAnswers(int nb, int count, AnswerOrderCriteria orderCriteria = AnswerOrderCriteria.ById);
+        public Task<(int nbPages, IEnumerable<T>? answers)> getAnswers(int nb, int count, AnswerOrderCriteria orderCriteria = AnswerOrderCriteria.ById);
         /// <summary>
         /// get some answers that answer to a question
         /// </summary>
diff --git a/WebApi/ManagerInterfaces/IChapterManager.cs b/WebApi/ManagerInterfaces/IChapterManager.cs
index 495dea1..0301eec 100644
--- a/WebApi/ManagerInterfaces/IChapterManager.cs
+++ b/WebApi/ManagerInterfaces/IChapterManager.cs
@@ -70,6 +70,6 @@ namespace ManagerInterfaces
         /// does not exist (<=> (nb-1)*count outside
         /// boundaries (0, getNbElement()-1)))
         /// </returns>
-        Task<(int nbPages, ReadOnlyCollection<T>? chapters)> getChapters(int nb, int count, ChapterOrderCriteria orderCriteria = ChapterOrderCriteria.ById);
+        Task<(int nbPages, IEnumerable<T>? chapters)> getChapters(int nb, int count, ChapterOrderCriteria orderCriteria = ChapterOrderCriteria.ById);
     }
 }
diff --git a/WebApi/ManagerInterfaces/ILobbyManager.cs b/WebApi/ManagerInterfaces/ILobbyManager.cs
index ba30722..d1291d7 100644
--- a/WebApi/ManagerInterfaces/ILobbyManager.cs
+++ b/WebApi/ManagerInterfaces/ILobbyManager.cs
@@ -57,7 +57,7 @@ namespace ManagerInterfaces
         /// does not exist (<=> (nb-1)*count outside
         /// boundaries (0, getNbElement()-1)))
         /// </returns>
-        public Task<(int nbPages, ReadOnlyCollection<T>? lobbies)> getLobbies(int nb, int count, LobbyOrderCriteria orderCriteria = LobbyOrderCriteria.ById);
+        public Task<(int nbPages, IEnumerable<T>? lobbies)> getLobbies(int nb, int count, LobbyOrderCriteria orderCriteria = LobbyOrderCriteria.ById);
         /// <summary>
         /// get a T element with an id
         /// </summary>
diff --git a/WebApi/ManagerInterfaces/IPlayerManager.cs b/WebApi/ManagerInterfaces/IPlayerManager.cs
index e5393e0..4d7cba2 100644
--- a/WebApi/ManagerInterfaces/IPlayerManager.cs
+++ b/WebApi/ManagerInterfaces/IPlayerManager.cs
@@ -62,7 +62,7 @@ namespace ManagerInterfaces
         /// does not exist (<=> (nb-1)*count outside
         /// boundaries (0, getNbElement()-1)))
         /// </returns>
-        public Task<(int nbPage, ReadOnlyCollection<T>? players)> getPlayers(int nb, int count, LobbyOrderCriteria orderCriteria = LobbyOrderCriteria.ById);
+        public Task<(int nbPage, IEnumerable<T>? players)> getPlayers(int nb, int count, LobbyOrderCriteria orderCriteria = LobbyOrderCriteria.ById);
         /// <summary>
         /// get a player
         /// </summary>
@@ -94,7 +94,7 @@ namespace ManagerInterfaces
         /// delete the lobby) if it is used by
         /// no player
         /// </returns>
-        public Task<ReadOnlyCollection<T>?> getPlayersInALobby(int idLobby);
+        public Task<IEnumerable<T>?> getPlayersInALobby(int idLobby);
         /// <summary>
         /// get the max score of a player in a chapter
         /// </summary>
diff --git a/WebApi/ManagerInterfaces/IQuestionManager.cs b/WebApi/ManagerInterfaces/IQuestionManager.cs
index a777522..5544d80 100644
--- a/WebApi/ManagerInterfaces/IQuestionManager.cs
+++ b/WebApi/ManagerInterfaces/IQuestionManager.cs
@@ -57,7 +57,7 @@ namespace ManagerInterfaces
         /// does not exist (<=> (nb-1)*count outside
         /// boundaries (0, getNbElement()-1)))
         /// </returns>
-        public Task<(int nbPages, ReadOnlyCollection<T>? questions)> getQuestions(int nb, int count, QuestionOrderCriteria orderCriteria = QuestionOrderCriteria.ById);
+        public Task<(int nbPages, IEnumerable<T>? questions)> getQuestions(int nb, int count, QuestionOrderCriteria orderCriteria = QuestionOrderCriteria.ById);
         /// <summary>
         /// get a T element with an id
         /// </summary>
@@ -110,7 +110,7 @@ namespace ManagerInterfaces
         /// or null if the chapter does not exist
         /// or the difficulty is not between 1 and 3
         /// </returns>
-        public Task<(int nbPages, ReadOnlyCollection<T>? questions)?> getQuestionsByChapterAndDifficulty(int idChapter, int difficulty, int nb, int count, QuestionOrderCriteria orderCriteria = QuestionOrderCriteria.ById);
+        public Task<(int nbPages, IEnumerable<T>? questions)?> getQuestionsByChapterAndDifficulty(int idChapter, int difficulty, int nb, int count, QuestionOrderCriteria orderCriteria = QuestionOrderCriteria.ById);
 
     }
 }