Walkthrough: Automatically Populating the Toolbox with Custom Components

If your components are defined by a project in the currently open solution, they will automatically appear in the Toolbox, with no action required by you. You can also manually populate the Toolbox with your custom components by using the Choose Toolbox Items Dialog Box (Visual Studio), but the Toolbox takes account of items in your solution's build outputs with all the following characteristics:


The Toolbox does not follow reference chains, so it won't display items that are not built by a project in your solution.

This walkthrough demonstrates how a custom component automatically appears in the Toolbox once the component is built. Tasks illustrated in this walkthrough include:

  • Creating a Windows Forms project.

  • Creating a custom component.

  • Creating an instance of a custom component.

  • Unloading and reloading a custom component.

When you are finished, you will see that the Toolbox is populated with a component that you have created.

Create the project

  1. In Visual Studio, create a Windows-based application project called ToolboxExample (File > New > Project > Visual C# or Visual Basic > Classic Desktop > Windows Forms Application).

  2. Add a new component to the project. Call it DemoComponent.

    For more information, see How to: Add New Project Items.

  3. Build the project.

  4. From the Tools menu, click the Options item. Click General under the Windows Forms Designer item and ensure that the AutoToolboxPopulate option is set to True.

Create an instance of a custom component

The next step is to create an instance of the custom component on the form. Because the Toolbox automatically accounts for the new component, this is as easy as creating any other component or control.

  1. Open the project's form in the Forms Designer.

  2. In the Toolbox, click the new tab called ToolboxExample Components.

    Once you click the tab, you will see DemoComponent.


    For performance reasons, components in the auto-populated area of the Toolbox do not display custom bitmaps, and the ToolboxBitmapAttribute is not supported. To display an icon for a custom component in the Toolbox, use the Choose Toolbox Items dialog box to load your component.

  3. Drag your component onto your form.

    An instance of the component is created and added to the Component Tray.

Unload and reload a custom component

The Toolbox takes account of the components in each loaded project, and when a project is unloaded, it removes references to the project's components.

  1. Unload the project from the solution.

    For more information about unloading projects, see How to: Unload and Reload Projects. If you are prompted to save, choose Yes.

  2. Add a new Windows Application project to the solution. Open the form in the Designer.

    The ToolboxExample Components tab from the previous project is now gone.

  3. Reload the ToolboxExample project.

    The ToolboxExample Components tab now reappears.

Next steps

This walkthrough demonstrates that the Toolbox takes account of a project's components, but the Toolbox is also takes account of controls. Experiment with your own custom controls by adding and removing control projects from your solution.

See also