项目通过类别进行识别，这帮助划分产品、特性或者项目交付的组件。
Projects are identified by a Category, which helps to classify the product, feature, or component that the project delivers.
在相同组件中定义的自订类别可以当做页面的根项目。
Custom classes cannot be used as the root element of a page if defined in the same assembly.
组件是视觉化样式项目类别的个别成员。
A part is a discrete member of a class of visual style elements.
例如，表示核取方块、选项按钮和按钮的视觉化样式项目，都视为“BUTTON”类别的组件。
For example, visual style elements that represent a check box, radio button, and push button are all considered parts of the "button" class.
如果衍生的工具箱项目类别会建立多个位于不同组件的元件，您必须确保这些组件的参考存在于专案中。
If your derived toolbox item class creates multiple components that are located in different assemblies, you must ensure that references to these assemblies exist in your project.
如果衍生的工具箱项目类别会建立多个位于不同组件的元件，您必须确保这些组件的参考存在于专案中。
If your derived toolbox item class creates multiple components that are located in different assemblies, you must ensure that references to these assemblies exist in your project.
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