The results of a JOIN operation are returned in either an instance of a class specified in the query or an instance of the __Generic class. If a single class is implied by the property list in the SELECT statement, the results are returned as instances of that class. If there are multiple classes, the results are returned as instances of the __Generic class.

The __Generic class is a generic container for the results of JOIN operations and COUNT operations. This class has no set definition. Its properties depend on its use at the time. For JOIN results, the properties are embedded objects representing the classes specified in the query, as the following example shows.

SELECT * FROM SMS_Package AS Pack

INNER JOIN SMS_Program AS Prog

ON Pack.PackageID = Prog.PackageID

The following example shows the __Generic class result of the above query.

Class __Generic

{

SMS_Package Pack;

SMS_Program Prog;

}

For COUNT results, the instance includes a Count property, as the following class shows.

Class __Generic

{

uint32 Count;

}

The class instances that are returned in a result set contain both system and class properties. However, embedded and lazy properties are not returned.

The system properties include those for the specified class and its derived classes. Because not all system properties are relevant to all queries, the value of a particular system property can be null.

The class properties that are returned depend on whether you specify a property list or the asterisk. If you specify a property list containing one or more class properties, the returned instance contains only the properties in the list. The property list should include the key properties for the class. When you invoke a query that does not specify key properties in the property list, the result set contains incomplete and therefore incorrect values for the system properties, __Path and __Relpath.

Tasks

How to Read Lazy Properties by Using Managed Code
How to Read Lazy Properties by Using WMI