Add an IDL property

The Add IDL Property wizard adds a property to an interface defined in an Interface Definition Library (IDL), such as in an ATL project that contains an .idl file. This wizard isn't available in projects that support MFC.

This wizard differs from the Add Property wizard and Add IDL MFC Property wizard in the following ways:

• The Add Property wizard adds a property to an interface in your project.
• The Add IDL MFC Property wizard is specific to MFC, ActiveX, or ATL projects that support MFC.

To add an IDL property

1. On the View menu, select Class View.

2. In Class View, right-click the name of the interface to which you want to add the property.

   Note

   You can also add properties to dispinterfaces, which, unless the project is attributed, are nested within the library node.

3. Right-click the name of the interface.

4. From the shortcut menu, select Add > Add Property.

5. In the Add IDL Property wizard, provide the information to create the property.

6. Select OK to add the property.

The Get and Put methods of the property are displayed as two icons in Class View under the interface where it's defined. Double-click either icon to view the property declaration in the .idl file.

For ATL interfaces, the Get and Put functions are added to the .cpp and .h files.

Add an IDL property wizard

The following section describes the UI that you'll use to add an IDL property:

• Property name

  Sets the name of the property.

• Property type

  The data type of the property.

• Return type

  For ATL interfaces, sets the return type for the property. For dual interfaces, HRESULT is always the return type, and select option is unavailable. For custom interfaces, you can select a return type from the list. HRESULT is still recommended, as it provides a standard way to return errors.

• Get function

  For ATL interfaces, creates the Get method for retrieving the property value. Select Get, Put, or both.

• Put function

  For ATL interfaces, creates the Put method for setting the property value. Select Get, Put, or both. If you select Put function, you can choose from the following two ways to implement the method:

  Option	Description
  propput	The PropPut function returns a copy of the object. propput is the default and the most common way to make the property writable.
  propputref	The PropPutRef function returns a reference to the object, rather than returning the copy of the object itself. Consider using propputref option for objects, such as large structs or arrays, that may have initialization overhead.

• Parameters

  Displays the list of parameters added to the property. Each item in the list consists of the parameter name, parameter type, and attributes.

  in indicates that the parameter is passed from the calling procedure to the called procedure. out indicates that the pointer parameter is returned from the called procedure to the calling procedure (from the server to the client).

• +

  Add a parameter. In Parameters, type the parameter type and name. For example, int x, and select OK.

• x

  Removes the selected parameter from Parameters.

• Pencil icon

  Edit the selected parameter.

• Attributes

1. helpcontext

   Specifies a context ID that lets the user view information about this property in the Help file. For more information, see helpcontext.

2. helpstring

   Specifies a character string that's used to describe the element to which it applies. By default, it's set to property Property name. For more information, see helpstring.

3. id

   Sets the numerical identifier that identifies the property. This option isn't available for properties of custom interfaces. For more information, see id.

• Additional attributes

Keywords in the Microsoft Interface Definition Language (MIDL) are described in detail in the MIDL language reference.

See also

Add Property
Add IDL MFC Property