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 will not 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.


The dialog boxes and menu commands you see might differ from those described in Help depending on your active settings or edition. To change your settings, choose Import and Export Settings on the Tools menu. For more information, see Customizing Development Settings in Visual Studio.

Creating the Project

The first step is to create the project and to set up the form.

To create the project

  1. Create a Windows-based application project called ToolboxExample.

    For more information, see How to: Create a Windows Application Project.

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

    For more information, see NIB: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.

Creating 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.

To create an instance of a custom component

  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.

Unloading and Reloading 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.

To experiment with the effect on the Toolbox of unloading and reloading components

  1. Unload the project from the solution.

    For more information about unloading projects, see NIB: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

General, Windows Forms Designer, Options Dialog Box
How to: Manipulate Toolbox Tabs
Choose Toolbox Items Dialog Box (Visual Studio)
Putting Controls on Windows Forms