Filtering Items Using a Comparison with a Keywords Property
The following discussion uses the Categories property as an example, but can apply as well to any multi-valued string property.
The Categories property of an item is of type keywords which can contain multiple values. When being compared to a comparison string in a filter, the Categories property behaves like a text string where values are separated by a comma and a space. This is true for filters using Microsoft Jet syntax or DAV Searching and Locating (DASL) syntax.
In a Jet query, you can only perform phrase-matching on a keywords property. You cannot perform starts-with or substring matching with a Jet query. Consider the following criteria for Table.Restrict:
string filter = "[Categories] = 'Partner'"
This Jet query will return rows for items where the Categories property for the item finds a phrase-match for Partner. It will return rows for items that are categorized as Partner, for items that are categorized as Partner and Important, and for items that are categorized as Tier1 Partner. It will not return rows for items that are categorized only as Partnership.
To overcome the limitations of keywords restrictions using the Jet query syntax, use DASL syntax which allows starts-with or substring restrictions. The following criteria string will find all items that contain Partner as a category, as one of the words in a category, and as the beginning part of a word in the category, such as the category Partnership:
criteria = "@SQL=" & Chr(34) _ & "urn:schemas-microsoft-com:office:office#Keywords" _ & Chr(34) & " ci_startswith 'Partner'"
You can also use a DASL query for equivalence matching in a multi-valued string property. Consider an example where items have one or more of the following four categories:
The DASL equivalence query:
criteria = "@SQL=" & Chr(34) _ & "urn:schemas-microsoft-com:office:office#Keywords" & Chr(34) _ & " = 'Book'"
returns any item that has Book as a category, including those categorized with multiple categories, where Book is one of the categories. The query does not return items that do not have Book as a category.
If the multi-valued property is added to the Table using a reference by namespace, the format of the values of the property is a variant array. To access these values, parse the elements in the array. Using the last example, this would also allow you to obtain the items that contain exactly Partner as a category.