Add related data custom field to content items

For each content item you create, for example BlogPosts, there are default fields, such as author and title. You can add custom fields that extend the information that the content item holds. You can also add a custom field of type Related data, for example, News. Thus, you can relate other content items to the BlogPosts item via the related data custom field. 

In the following example, you add programmatically the News custom field as related data to the BlogPosts content item:

In the AddRelatedDataFieldToContext method above, you:

1. Specify:
   1. Full name of the content type to which you add the custom field. In the example above, this is the BlogPost content item: "Telerik.Sitefinity.Blogs.Model.BlogPost,Telerik.Sitefinity.ContentModules"
   2. Second parameter as a Dictionary collection of relatedFields.
      The Dictionary collection stores the related data fields thus associating the custom field name to the related data field object.
2. Create an instance of the CustomFieldsContext class and pass the content type as a parameter.
3. Create an instance of the WcfField class to add information about the field, its database mapping, and definition.
4. Set the following properties of the WcfField class:
   • Name
     Gets or sets the name of the field. The value must not contain spaces or any special characters.
   • ContentType
     Gets or sets the type of the content the field belongs to.
   • FieldTypeKey
     Gets or sets the UserFriendlyDataType value for the field. The class represents an enumeration. In this example, you set the value to RelatedData. 
   • IsCustom
     Indicates whether the field is a custom field.
   • Definition
     Gets or sets a field definition. You must create an instance of the WcfFieldDefinition class. This class wraps the information about the field definition. The definition specifies the way the field is represented in the user interface. Set the following properties of the WcfFieldDefinition class:
     • Title
       Gets or sets the display title of the field.
     • FieldName
       Gets or sets the name of the field. The value must not contain spaces or any special characters.
     • FieldType
       Gets or sets the field control type that is used to represent the field in user interface.
     • AllowMultipleSelection
       Gets or sets whether the control supports multiple selection.
     • FrontendWidgetTypeName
       Gets or sets the type name of the frontend widget.
     • RelatedDataProvider
       Gets or sets the provider of the related data.
     • RelatedDataType
       Gets or sets the type of the related data. In this example, you specify the type as NewsItem.
5. Add the created custom field to the CustomFieldContext instance using AddOrUpdateCustomFields method.
6. Save the context to the database and restart the Sitefinity CMS application.