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| 1 | +--- |
| 2 | +description: "Learn more about: Use a Microsoft Visual Studio wizard to add a method to an interface definition language (IDL) interface in your project" |
| 3 | +title: "Add an IDL method" |
| 4 | +ms.date: "04/13/2022" |
| 5 | +f1_keywords: ["vc.codewiz.method.overview", "vc.codewiz.method.idlattrib"] |
| 6 | +helpviewer_keywords: ["add IDL method wizard [C++]", "IDL methods [C++], adding", "methods [C++], adding using wizards", "IDL attributes, add an IDL method wizard"] |
| 7 | +ms.custom: devdivchpfy22 |
| 8 | +--- |
| 9 | + |
| 10 | +# Add an IDL method |
| 11 | + |
| 12 | +The **Add IDL Method** wizard adds a method to an Interface Definition Library (IDL) interface, such as in an ATL project that contains an IDL file. This wizard isn't available in projects that support MFC. |
| 13 | + |
| 14 | +This wizard differs from the [**Add method**](adding-a-method-visual-cpp.md) wizard and the [**Add IDL MFC method**](../mfc/reference/add-idl-mfc-method-wizard.md) wizard in the following ways: |
| 15 | + |
| 16 | +- The **Add method** wizard adds a method to an interface in your project and can update the class associated with the interface. |
| 17 | +- The **Add IDL MFC method** wizard is specific to MFC, ActiveX, or ATL projects that support MFC. |
| 18 | + |
| 19 | +## Add a method to your IDL interface |
| 20 | + |
| 21 | +1. On the **View** menu, select **Class View**. |
| 22 | + |
| 23 | +1. In the **Class View** pane, expand the project node to display the IDL interface (`.idl`file) to which you want to add the method. |
| 24 | + |
| 25 | +1. Right-click the name of the interface. |
| 26 | + |
| 27 | +1. On the shortcut menu, select **Add** > **Add Method**. |
| 28 | + |
| 29 | +1. In the **Add IDL Method** wizard, provide the information to create the method. |
| 30 | + |
| 31 | +1. Select **OK** to add the method. |
| 32 | + |
| 33 | +### User Interface element list |
| 34 | + |
| 35 | +The following section describes the wizard interface that you'll use to add a method: |
| 36 | + |
| 37 | +:::image type="content" source= "media/add-interface-definition-library-method-wizard.png" alt-text="Screenshot of adding a method using the wizard. Shows two parameters: [ in ] int i and [ in ] float f. Return type is HRESULT. Infer in out parameter values from type is selected."::: |
| 38 | + |
| 39 | +- **Method name** |
| 40 | + |
| 41 | + Provide a name for the method. |
| 42 | + |
| 43 | +- **Return type** |
| 44 | + |
| 45 | + The data type returned by the method. The standard way to return error codes from methods defined in an interface is with a `HRESULT`. |
| 46 | + |
| 47 | + The following table describes the different kinds of interfaces that you can add a method to, and the allowed return type. For dual and custom interfaces, the return type must be `HRESULT` and the wizard won't allow you to change it. |
| 48 | + |
| 49 | + |Interface kind|Return type| |
| 50 | + |--------------------|-----------------| |
| 51 | + |[Dual interface](/windows/win32/winauto/dual-interfaces--iaccessible-and-idispatch)|`HRESULT`. Unchangeable.| |
| 52 | + |[Custom interface](/windows/win32/winauto/custom-user-interface-elements)|`HRESULT`. Unchangeable.| |
| 53 | + |Local custom interface|Provide your own return type or select it from the drop-down list.| |
| 54 | + |[Dispinterface](/windows/win32/midl/dispinterface)|Provide your own return type or select it from the drop-down list.| |
| 55 | + |
| 56 | +- **Parameters** |
| 57 | + |
| 58 | + Displays the method's parameters, modifiers, and types. |
| 59 | + |
| 60 | +- **+** |
| 61 | + |
| 62 | + Add a parameter. In **Parameters**, type the parameter type, name, and any modifiers. For example, `[in] int i`, and choose **OK**. |
| 63 | + |
| 64 | +- **x** |
| 65 | + |
| 66 | + Removes the selected parameter from the **Parameters** list. |
| 67 | + |
| 68 | +- **Infer in/out parameters values from types** |
| 69 | + |
| 70 | + Inserts the `[in]` or `[out]` attribute based on the parameter's type. |
| 71 | + |
| 72 | +- **Set the last parameter as the return value (retval)** |
| 73 | + |
| 74 | + The last parameter will be treated as the method's return value. |
| 75 | + |
| 76 | +- **Attributes** |
| 77 | + |
| 78 | + The following attributes are also described in the [MIDL Reference](/windows/win32/midl/midl-language-reference.md). |
| 79 | + |
| 80 | + - `id` |
| 81 | + |
| 82 | + Sets the numeric ID that identifies the method. For more information, see [`id`](/windows/win32/Midl/id). |
| 83 | + |
| 84 | + - `call_as` |
| 85 | + |
| 86 | + Specifies the name of the remote method to map to this local method. For more information, see [`call_as`](/windows/win32/Midl/call-as). |
| 87 | + |
| 88 | + - `helpcontext` |
| 89 | + |
| 90 | + Specifies a context ID that lets the user view information about this method in the Help file. For more information, see [`helpcontext`](/windows/win32/Midl/helpcontext). |
| 91 | + |
| 92 | + - `helpstring` |
| 93 | + |
| 94 | + Specifies the character string used to describe the element to which it applies. For more information, see [`helpstring`](/windows/win32/Midl/helpstring). |
| 95 | + |
| 96 | +- **Additional attributes** |
| 97 | + |
| 98 | + - `hidden` |
| 99 | + |
| 100 | + Indicates that the item exists but shouldn't be displayed in a user-oriented browser. For more information, see [`hidden`](/windows/win32/Midl/hidden). |
| 101 | + |
| 102 | + - `local` |
| 103 | + |
| 104 | + Specifies that an interface or function isn't remote. For more information, see [`local`](/windows/win32/Midl/local). |
| 105 | + |
| 106 | + - `restricted` |
| 107 | + |
| 108 | + Specifies that a library, or member of a module, interface, or dispinterface can't be called arbitrarily. For more information, see [`restricted`](/windows/win32/Midl/restricted). |
| 109 | + |
| 110 | + - `source` |
| 111 | + |
| 112 | + Indicates that a member of a [`coclass`](/windows/win32/Midl/coclass), property, or method is a source of events. For a member of a `coclass`, this attribute means that the member is called rather than implemented. For more information, see [`source`](/windows/win32/Midl/source). |
| 113 | + |
| 114 | +## See also |
| 115 | + |
| 116 | +[Add a method wizard](adding-a-method-visual-cpp.md)\ |
| 117 | +[Add an IDL MFC method wizard](../mfc/reference/add-idl-mfc-method-wizard.md) |
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