--- title: Membership slug: cms-12/api/groups-membership docTags: createdAt: 2026-08-07T16:45:44.000Z --- A group is a named aggregation of users and content. Users are associated with a group by adding them as members. Members are represented by the `Member` class. Members are managed through a service implementing the interface `IMemberService`. This service provides the ability to persist, retrieve, and remove `Members` that you define. ## Access an IMemberService When the `Groups` feature is installed on an Optimizely Content Management System (CMS) site with the feature's site integration package; you can get an instance of this service from the inversion of control (IoC) container. Example: ```csharp var memberService = EPiServer.ServiceLocation.ServiceLocator.Current.GetInstance(); ``` When the feature is installed on a non-Optimizely CMS site, you can get an instance of a service from the default factory class provided within the package. ```csharp var factory = new EPiServer.Social.Groups.DefaultMemberServiceFactory(); var memberService = factory.Create(); ``` ## Add a member To add a member, use the `Add(Member)` method of the `IMemberService`. This method accepts an instance of the `Member` class, and returns a reference to an instance of that class, populated with any additional, system-generated data (for example, a unique ID). ```csharp IMemberService memberService; GroupId idOfExistingGroup; Reference user; // ... var member = new Member(user, idOfExistingGroup); memberService.Add(member); ``` If the identified group cannot be found, a `GroupDoesNotExistException` is thrown. If the member already exists, a `DuplicateMemberException` is thrown. The above example invokes the request to add a member synchronously. An example of adding a member asynchronously using the asynchronous overload with C#'s async and await keywords is described below. ```csharp private async Task AddMemberAsync(IMemberService memberService) { GroupId idOfExistingGroup; Reference user; // ... var member = new Member(user, idOfExistingGroup); var addMemberTask = memberService.AddAsync(member); //Do other application specific work in parallel while the task executes. //.... //Wait until the task runs to completion. var addedMember = await addMemberTask; return addedMember; } ``` ## Validate a member To validate that a user is a member of a group, use the `IsMember(GroupId,Reference)` method of the `IMemberService`. This method accepts an instance of the `GroupId` class, identifying the target group, and an instance of the `Reference` class, identifying the target user. The method returns a Boolean, indicating whether or not the identified user is a member of the identified group. ```csharp IMemberService memberService; GroupId idOfExistingGroup; Reference user; // ... bool isMember = memberService.IsMember(idOfExistingGroup, user); ``` In the above example, the request to validate if a user is a group member is invoked synchronously. An example of validating a user's membership in a group asynchronously using the asynchronous overload with C#'s async and await keywords is described below. ```csharp private async Task ValidateMemberAsync(IMemberService memberService) { GroupId idOfExistingGroup; Reference user; // ... var isMemberTask = memberService.IsMemberAsync(idOfExistingGroup, user); //Do other application specific work in parallel while the task executes. //.... //Wait until the task runs to completion. var isValid = await isMemberTask; return isValid; } ``` ## Remove a member To remove a specific instance of Member, which was previously added through the platform, use the `Remove(MemberId)` class. This method accepts an instance of the `MemberId` class, which identifies the `MemberId` to be removed. The result is the deletion of the `Member` corresponding to that ID. ```csharp IMemberService memberService; // ... // Construct or retrieve an ID for an existing member. var memberId = MemberId.Create("..."); memberService.Remove(memberId); ``` The above example invokes the request to remove a member synchronously. An example of removing a member asynchronously using the asynchronous overload with C#'s async and await keywords is described below. ```csharp private async Task RemoveMemberAsync(IMemberService memberService) { //... // Construct or retrieve an ID for an existing member. var memberId = MemberId.Create("..."); var removeMemberTask = memberService.RemoveAsync(memberId); //Do other application specific work in parallel while the task executes. //.... //Wait until the task runs to completion. await removeMemberTask; } ``` ## Retrieve a member You can retrieve a specific instance of a `Member`, which was previously added through the platform by using the `Get(MemberId)` method of `IMemberService`. This method accepts an instance of the `MemberId` class, which identifies the `Member` to retrieve. It returns the instance of the `Member` class corresponding to that identifier. ```csharp IMemberService memberService; //... // Construct a MemberId corresponding to the desired member var memberId = MemberId.Create("..."); var member = memberService.Get(memberId); ``` If the requested `Member` cannot be found, a `MemberDoesNotExistException` is thrown. The above example invokes the request to retrieve a member synchronously. An example of retrieving a member asynchronously using the asynchronous overload with C#'s async and await keywords is described below. ```csharp private async Task GetMemberAsync(IMemberService memberService) { //... // Construct a MemberId corresponding to the desired member var memberId = MemberId.Create("..."); var getMemberTask = memberService.GetAsync(memberId); //Do other application specific work in parallel while the task executes. //.... //Wait until the task runs to completion. var member = await getMemberTask; return member; } ``` To retrieve a collection of members that were previously added through the platform, use the `Get(Criteria)` method. This method accepts an instance of `Criteria`, which contains the specifications to retrieve desired `Members`. The `Filter` property of the `Criteria` class accepts an instance of the `MemberFilter` class. This class contains the specifications that let you refine the result set of Members you want to retrieve. The properties of the `MemberFilter` class include: - `Group` – Assigning a value (`GroupId`) to this property refines a result set to Members of the identified group. - `MemberIds` – Assigning a value (`IEnumerable`) to this property refines a result set to Members identified in the collection. - `Role` – Assigning a value (`RoleId`) to this property refines a result set to Members assigned the identified role. - `User` – Assigning a value (`Reference`) to this property refines a result set to Members associated with the identified user. The specifications of the `MemberFilter` may be applied in conjunction with one another. Each specification, assigned a value in the filter, further refines the result set (a logical AND). The example below demonstrates the retrieval of a result page of `Members` assigned to a group. ```csharp IMemberService memberService; Group existingGroup; // ... var criteria = new Criteria { Filter = new MemberFilter { Group = existingGroup.Id } }; var pageOfMembers = memberService.Get(criteria); ``` In the above examples, the request to retrieve members is invoked synchronously. An example of retrieving members asynchronously using the asynchronous overload with C#'s async and await keywords is described below. ```csharp private async Task> GetMembersAsync(IMemberService memberService) { Group existingGroup; // ... var criteria = new Criteria { Filter = new MemberFilter { Group = existingGroup.Id } }; var getMembersTask = memberService.GetAsync(criteria); //Do other application specific work in parallel while the task executes. //.... //Wait until the task runs to completion. var pageOfMembers = await getMembersTask; return pageOfMembers; } ``` The `MemberSortFields` class exposes a set of fields upon which a result set of members may be ordered. You can apply these fields to construct sorting rules associated with your criteria. These fields include: - `MemberSortFields.Group` - `MemberSortFields.Id` - `MemberSortFields.User` The example below demonstrates how to apply sorting rules to order your result set by group ID in ascending order. ```csharp var criteria = new Criteria { // ... OrderBy = new List { new SortInfo(MemberSortFields.Group, true) } }; ``` For details on using criteria, including information on paging and sorting, see *Criteria* in [Discover the platform](docId\:NKmGS-fLtRQIYLEWZfb69). ## Extend members with composites A `Member` is a relationship between a user and a group. You may need to associate additional information with members to describe and shape them further. Continuing an earlier example, where a group represents an athletic team, a member may represent a player on the team. You might want to capture information identifying the player's uniform number or primary position. Just as you can extend a `Group` with data of your design, a `Member` may also be extended by creating a Composite. For an introduction to Composites, see *Composites* in [Discover the platform](docId\:NKmGS-fLtRQIYLEWZfb69). This section explains the synchronous and asynchronous APIs of the member service that support extending members with composites. ### Add a composite member To save a Composite Member that you defined, use the `Add(Member, TExtension)` method of the `IMemberService`. This method accepts an instance of the `Member` class and an instance of `TExtension`. It returns an instance of `Composite`. Consider the following class, which represents a sample of extension data: ```csharp public class Player { public int UniformNumber { get; set; } public string Position { get; set; } } ``` In the example below, a `Member` is composed with an instance of this extension class: ```csharp IMemberService memberService; GroupId existingGroup; Reference user; // ... var member = new Member(user, existingGroup); var extension = new Player { UniformNumber = 2, Position = "Shortstop" }; var compositeMember = memberService.Add(member, extension); ``` The above example invokes the request to add a member synchronously. An example of adding a member asynchronously using the asynchronous overload with C#'s async and await keywords is described below. ```csharp private async Task> AddMemberAsync(IMemberService memberService) { // ... GroupId existingGroup; Reference user; // ... var member = new Member(user, existingGroup); var extension = new Player { UniformNumber = 2, Position = "Shortstop" }; var addMemberTask = memberService.AddAsync(member, extension); //Do other application specific work in parallel while the task executes. //.... //Wait until the task runs to completion. var compositeMember = await addMemberTask; return compositeMember; } ``` ### Update a composite member To update a specific instance of a Composite Member, which was previously added through the platform, use the `Update(MemberId, TExtension)` method of the `IMemberService`. This method accepts an instance of the `MemberId` class and an instance of `TExtension`. It returns an instance of `Composite`. Consider the following class, which represents a sample of extension data: ```csharp public class Player { public int UniformNumber { get; set; } public string Position { get; set; } } ``` For this example, the below `IMemberService` is properly implemented ```csharp IMemberService memberService; // ... // Construct a MemberId corresponding to the desired member MemberId existingMemberId; var newExtension = new Player { UniformNumber = 3, Position = "Pitcher" }; memberService.Update(existingMemberId, newExtension); ``` The above example invokes the request to update a member synchronously. An example of updating a member asynchronously using the asynchronous overload with C#'s async and await keywords is described below. ```csharp private async Task> UpdateMemberAsync(IMemberService memberService) { // ... // Construct a MemberId corresponding to the desired member MemberId existingMemberId; var newExtension = new Player { UniformNumber = 3, Position = "Pitcher" }; var updateMemberTask = memberService.UpdateAsync(existingMemberId, newExtension); //Do other application specific work in parallel while the task executes. //.... //Wait until the task runs to completion. var updatedMember = await updateMemberTask; return updatedMember; } ``` ### Retrieve a composite member To retrieve a specific instance of a Composite Member, which was previously added through the platform, use the `Get(MemberId)` method. This method accepts an instance of the `MemberId` class, which identifies the `Member` to retrieve. It returns the instance of the `Composite` class corresponding to that identifier. ```csharp IMemberService memberService; //... // Construct a MemberId corresponding to the desired member var memberId = MemberId.Create("..."); var compositeMember = memberService.Get(memberId); ``` If a Composite Member with the specified ID and extension type cannot be found, a `MemberDoesNotExistException` is thrown. The above example invokes the request to retrieve a member synchronously. An example of retrieving a member asynchronously using the asynchronous overload with C#'s async and await keywords is described below. ```csharp private async Task> GetMemberAsync(IMemberService memberService) { //... // Construct a MemberId corresponding to the desired member var memberId = MemberId.Create("..."); var getMemberTask = memberService.GetAsync(memberId); //Do other application specific work in parallel while the task executes. //.... //Wait until the task runs to completion. var compositeMember = await getMemberTask; return compositeMember; } ``` To retrieve a collection of Composite Members, which were previously added through the platform, use the `Get(CompositeCriteria)` method. This method accepts an instance of `CompositeCriteria[MemberFilter,TExtension]`, which contains the specifications necessary to retrieve the desired Members. The `Filter` property of the `CompositeCriteria` class accepts an instance of the `MemberFilter` class. This class contains the specifications that let you refine the result set of `Members` that you want to retrieve. The `ExtensionFilter` property of the `CompositeCriteria` class accepts a `FilterExpression` that lets you specify a Boolean expression to refine the result set further by values represented within your extension data. (For information on this type of filter, see *Composite Criteria* and *Filtering Composites* in [Discover the platform](docId\:NKmGS-fLtRQIYLEWZfb69). Consider the following class, which represents a sample of extension data: ```csharp public class Player { public int UniformNumber { get; set; } public string Position { get; set; } } ``` In the example below, a page of Members composed with Player is retrieved, where the players have a position of "Shortstop": ```csharp IMemberService memberService; // ... var criteria = new CompositeCriteria { ExtensionFilter = FilterExpressionBuilder .Field(e => e.Position).EqualTo("Shortstop") }; var pageOfMembers = memberService.Get(criteria); ``` In the above example, the request to retrieve members is invoked synchronously. An example of retrieving members asynchronously using the asynchronous overload with C#'s async and await keywords is described below. ```csharp private async Task>> GetMembersAsync(IMemberService memberService) { // ... var criteria = new CompositeCriteria { ExtensionFilter = FilterExpressionBuilder .Field(e => e.Position).EqualTo("Shortstop") }; var getMembersTask = memberService.GetAsync(criteria); //Do other application specific work in parallel while the task executes. //.... //Wait until the task runs to completion. var pageOfMembers = await getMembersTask; return pageOfMembers; } ``` The fields of your extension data may also be applied when sorting your result set. The example below demonstrates the use of an extension data field in defining a sorting rule. ```csharp var criteria = new CompositeCriteria { // ... OrderBy = new List { new SortInfo(new SortField(FilterExpressionBuilder .Field(e => e.UniformNumber)), true) } }; ``` For details about using criteria, including information on paging and sorting, see *Criteria* in [Discover the platform](docId\:NKmGS-fLtRQIYLEWZfb69).