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## How it works

`EPiServer.Core.IContentData` is the base interface that all content models implement. All content types, except `BlockData`, also implement the `EPiServer.Core.IContent` interface, which is required for a content instance to have a unique ID and its own lifecycle (that is, can be loaded/saved individually). Through the `EPiServer.IContentRepository`, you can perform CRUD (Create, Read, Update, Delete) operations on content instances implementing `EPiServer.Core.IContent`, for example, listing and move.

There are also many additional metadata interfaces a content type can implement that define the characteristics of the content type. Here is a list of the existing metadata interfaces with a description on the purpose of each interface and which properties they contain.

## Usage 

Because some of the interfaces are optional, a recommended pattern when working with a "general" `IContent` instance is to use the **is **or **as** operators to check if the instance implements an interface, as in this example:



### Shared blocks
`BlockData` does not implement `IContent`, while shared block instances still have their own identity defined on `IContent`. This is accomplished so that during runtime, when a shared block instance is created (for example, through a call to `IContentRepository.GetDefault<T>` where T is a type inheriting from BlockData), the CMS creates a new .NET type inheriting T using a technique called **mixin** where the new generated subclass will implement some extra interfaces (including IContent).
That means that a shared block instance of T will implement `IContent` while an instance of T that is a property on a Page will not.
## IContentData
Base interface for all content models. It contains a backing `PropertyDataCollection` that is used when loading/saving data from database.
MemberTypeDescription
`Property` `PropertyDataCollection`Contains backing data for properties used by the content instance.
## IContent
Base interface for all content models that can have an own identity, and hence can be loaded/saved individually. `IContent` inherits `IContentData`. Note that `ContentLink.ID` and `ContentGuid` is the same for all language branches for a content item. So the combination of `ContentLink`/`ContentGuid` and `ILocale.Language` uniquely specifies the content instance (given that the content implements `ILocalizable`). All built-in base content types, except `BlockData`, implement `IContent`. Shared block instances implement `IContent` (and most other metadata interfaces) at runtime.
MemberTypeDescription
`Name` `string`The name of the content instance.
`ContentLink``ContentReference`The identifier of the content instance. WorkID specifies an optional version ID, in case the instance represents a specific version.
`ContentGuid``Guid`A GUID-based identifier for the content instance.
`ParentLink``ContentReference`The parent identifier (in a tree structure) for the content instance.
`ContentTypeID``int`An identifier that specifies which content type the content is an instance of.
`IsDeleted``bool`Indicates if the content instance is in the wastebasket.
`Property ``PropertyDataCollection`Inherited from `IContentData`.
## IVersionable
An optional interface for content that supports different versions for each language branch. There can only be at most one version published at each time. All built-in types, except `ContentFolder`, implement `IVersionable`. See [Content versions](🔗) for more information regarding versions.
MemberTypeDescription
`Status ``VersionStatus`Specifies the status of the content version.
`IsPendingPublish``bool`Specifies if there is any published version for the current language branch.
`StartPublish``DateTime?`Optional value that specifies when the content is/was published.
`StopPublish``DateTime?`Optional value that specifies when the content is/was depublished.
## ILocale
An optional interface for content that specifies which language a specific content instance has. All built-in types except `ContentFolder` implements `ILocale`.
MemberTypeDescription
`Language ``CultureInfo`Specifies the language of a content instance. `CultureInfo.InvariantCulture` means that the content instance is not culture specific.
## ILocalizable
An optional interface for content that support multiple language branches. Inherits `ILocale`. All built-in types, except `ContentFolder` and `MediaData`, implement `ILocalizable`.
MemberTypeDescription
`Language ``CultureInfo`Inherits from `ILocale`.
`MasterLanguage``CultureInfo`Specifies which language version that contains the none language-specific properties.
`ExistingLanguages``IEnumerable<CultureInfo>`Specifies all existing language branches for this content.
## IReadOnly/IReadOnly<T>
An optional interface for content that support read-only instances. It is highly recommended that content types implement `IReadOnly`, which ensures the integrity of the content instances when instances are served from cache and hence reused across different requests. All built-in base content classes implement `IReadOnly`.
MemberTypeDescription
`IsReadOnly``bool`Specifies if the current instance is read-only.
`void MakeReadOnly()``Method`Makes an instance read-only.
`object/T CreateWritableClone()``Method`Creates a writable clone from a read-only instance.
## IModifiedTrackable
An optional interface for content instances that support modified tracking. There is a high performance gain during save operations if `IModifiedTrackable` since then only data that has actually changed needs to be persisted. All built-in base content classes implement `IModifiedTrackable`.
MemberTypeDescription
`IsModified``bool`Specifies it the current instance is modified.
`void ResetModified()``Method`Sets the content instance in a none modified state.
## IChangeTrackable
An optional interface for content instances that support tracking of changes. All built-in base content classes implement `IChangeTrackable`.
MemberTypeDescription
`IsModified``bool`Specifies if the current instance is modified.
`void ResetModified()``Method`Sets the content instance in a none modified state.
## IContentSecurable
An optional interface for content instances that support access checks. All built-in base content classes implement `IContentSecurable`.
MemberTypeDescription
`IContentSecurityDescriptor GetContentSecurityDescriptor()``Method`Gets the security descriptor for the content instance where access rights can be checked.
## IRoutable
An interface that content items that should be routable through a content URL should implement. All built-in base content classes, except shared blocks, implement `IRoutable`.
MemberTypeDescription
`RouteSegment``string`Specifies the route segment that is used for the content instance in the hierarchical content url.
## ICategorizable
An interface that content items that should be possible to categorize should implement. All built-in base content classes, except content folders, implement `ICategorizable`.
MemberTypeDescription
`Category``CategoryList`A list of all categories that this content instance is categorized as.
## IInitializableContent
An optional interface that content items that can be implemented if default values should be added when a new instance of the content type is created.
MemberTypeDescription
`void SetDefaultValues(ContentType contentType)``Method`Called when a new instance of the content type is created.
## IExportable
An optional interface that specifies how a content instance should be handled during export.
MemberTypeDescription
`ShouldBeImplicitlyExported``bool`Specifies whether this instance should be implicitly added to export package when referenced by some entity that is exported.