Microsoft KB Archive/107546
Article ID: 107546
Article Last Modified on 8/9/2004
- Microsoft OLE 2.03
- Microsoft OLE 4.0, when used with:
- Microsoft Windows NT 4.0
- Microsoft Windows NT 3.51 Service Pack 5
- Microsoft Windows 95
This article was previously published under Q107546
Collect.exe demonstrates how to create an OLE automation collection object.
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The collection object implements the following methods and properties: Add Method, Count Property, Item Property, NewEnum Property, and Remove Method.
Error handling in the collection object involves raising exceptions. CreateStdDispatch does not allow exceptions to be raised, so the collection object implements the IDispatch interface using DispGetIDsOfNames and DispInvoke.
Description: Adds the indicated item to the collection. If an object is created, it should be returned. Arguments: Varies. It can be a pointer to the object that is to be added or it can the information required to create the object. Return type: Varies. If no object is created, the return type should be void. If an object is created, the return type should be VT_DISPATCH.
NOTE: The Add method is not appropriate for all collections, so it is not required. For many application-created collections, objects are automatically added to the collection for the user.
Description: Returns the number of items in the collection. Read-only property. Arguments: None. Return type: VT_I4.
Description: Returns the indicated item in the collection. Argument: Specifies the index. Some collections allow various types of indexing. For example, this sample allows an integer or string to be specified as an index. Return type: VT_DISPATCH.
NOTE: Item is the default value for the object, so it should have the special DISPID, DISPID_VALUE. MkTypLib automatically assigns this DISPID if the default attribute is specified in the ODL file.
Description: Returns an enumerator that supports IEnumVariant for the items currently in the collection. Read-only property. Arguments: None. Return type: VT_UNKNOWN.
NOTE: NewEnum will not be accessible to users and must have the restricted attribute in the ODL file. The NewEnum method must have a special DISPID, DISPID_NEWENUM. The defining characteristic of a collection is the ability for a user to iterate over the items in it. Some languages will have built- in support for collections. The NewEnum method allows an OLE automation controller to support "for each" iteration over a collection:
For Each Item In Collection Debug.Print Item.Text Next Item
OLE automation controllers that support "for each" iteration will call the NewEnum method on the collection object and then QueryInterface on the resulting IUnknown to get the desired IEnumVariant.
Description: Removes the specified item from the collection. Argument: Specifies the index. Some collections allow various types of indexing. For example, this sample allows an integer or string to be specified as an index. Return type: void.
NOTE: The object is not deleted. It is simply removed from the collection. Remove should support the same kinds of indexing as the Item() method for the same collection. The Remove method is not appropriate for all collections, so it is not required. For many application-created collections, objects are automatically removed the collection for the user.
The collection sample application object exposes the following:
ProgID : Collection.Application
Method and Property Names Notes ----------------------------------------------------------- [App Object] Collection (read only prop) Returns empty collection. New Item (method) Creates and returns new item. [Item Object] Text (default prop) Sets and returns string. [Collection Object] See above for exposed properties and methods.
Update the path in HELLO.REG to the current location of the object and the type libraries.
Requires OLE version 2.01 or later.
Include device=vmb.386 in the [386Enh] section of SYSTEM.INI.
NOTE: vmb.386 can be found in \OLE2\BIN. Run WXSERVER.EXE from \OLE2\BIN before running the makefile.
Additional query words: AutoCtrl Collect
Keywords: kbinfo kbdownload kbdocfix kbfile kbautomation kbsample KB107546