DOC: Collect.exe - OLE Automation Collection

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Summary
Collect.exe demonstrates how to create an OLE automation collection object.
More information
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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.

Add Method

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.

Count Property

Description:     Returns the number of items in the collection. Read-only                 property.Arguments:       None.Return type:     VT_I4.				

Item Property

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.

_NewEnum Property

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.

Remove Method

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.

To Run

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.

To Compile

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.
AutoCtrl Collect
Properties

Article ID: 107546 - Last Review: 01/10/2015 10:55:35 - Revision: 5.0

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