This feature will be removed in a future version of Microsoft SQL Server. Avoid using this feature in new development work, and plan to modify applications that currently use this feature.
The FullTextKeyColumn property returns the identifier of the column selected for row identification for Microsoft Search.
Microsoft Search requires a single column to identify rows participating in an index that supports full-text query. The column designated must contain unique, non-null values and must participate in a table's PRIMARY KEY constraint or UNIQUE index.
Use UniqueIndexForFullText to configure Microsoft Search full-text index key column use.