Gets an SPFieldLinkCollection that represents the collection of column, or field, references in the content type.
Assembly: Microsoft.SharePoint (in Microsoft.SharePoint.dll)
If you want to track certain item metadata in a content type, you can reference a column that represents that metadata. However, you cannot create a column in a content type; you must create the column and then reference it in the content type definition. As a result, when you add a column to a content type, the content type does not contain a column, or field; it contains a column, or field, reference.
For more information, see Fields and Field References.
The SPFieldCollection object provides developers a way to get a combined view of a column's attributes, as they exist in that content type. Each SPField object represents all the attributes of a column, or field, definition, combined with those attributes that have been overridden in the field reference for that content type.
When you access a SPField in a content type, Windows SharePoint Services merges the field definition with the field reference, and returns the resulting SPField object to you. This prevents developers from having to look up a field definition, and then look up all the attributes in the field definition overridden by the field reference for that content type.
Because of this, there is a 1-to-1 correlation between the items in the SPFieldLinkCollection and SPFieldCollection objects. For each SPFieldLink you add to a content type, Windows SharePoint Services adds a corresponding SPField object that represents the merged view of that column as it's defined in the content type.
The following example is part of a console application that creates a new field and adds it to the site’s SPFieldCollection. Then the application creates a new SPFieldLink with a reference to the new column and adds it to a content type’s [SPFieldLinkCollection] collection. Finally, the application updates the content type, committing the changes to the database.
Note that a field must exist in the site’s field collection before it can be used to create an SPFieldLink object.
SPSite site = new SPSite("http://localhost"); SPWeb web = site.OpenWeb(); // Get a reference to the site content type collection. SPContentTypeCollection contentTypes = web.ContentTypes; // Create a Customer content type derived from the Contact content type. SPContentType contentType = new SPContentType(contentTypes["Contact"], contentTypes, "Customer"); // Add the content type to the site collection. contentTypes.Add(contentType); // Get a reference to the site fields (columns) collection. SPFieldCollection siteFields = web.Fields; // Create a new field (column) and add it to the site collection. string fieldName = siteFields.Add("Last Order", SPFieldType.DateTime, false); // Create a reference to the new field. SPFieldLink fieldLink = new SPFieldLink(siteFields.GetField(fieldName)); // Add the field reference to the content type. contentType.FieldLinks.Add(fieldLink); // Commit changes to the content type. contentType.Update(); // Clean up web.Dispose(); site.Dispose();