# Documenting a component library
> Register your own Blazor components, preview them live, and generate their props tables.
Source: https://shelldocs.shellui.dev/docs/guides/component-libraries
ShellDocs is built to document Blazor components with the components themselves on the page. This guide takes a library from "referenced by the docs project" to live previews with generated props tables.
## Reference and register
Reference the library from the docs project, then register its components so their tags work in markdown.
```csharp
builder.Services.AddShellDocs(o =>
{
o.RegisterComponentsFromAssembly();
});
```
The type argument is any type from the assembly. Every public, concrete component in it is registered under its class name.
| Call | Registers |
|---|---|
| `RegisterComponentsFromAssembly()` | Every public component in the marker's assembly |
| `RegisterComponentsFromAssembly("MyLib.Forms")` | Only components whose namespace starts with the prefix |
| `RegisterComponentsFromAssembly(t => …)` | Only components the filter accepts |
| `RegisterComponent()` | One component |
| `RegisterComponent("Btn")` | One component under a different tag name |
Mark a public component with `[ShellDocsIgnore]` to keep it out of markdown.
## Preview a component
Once registered, a component tag works in a `razor:preview` fence. The fence shows the component and its source.
````markdown
```razor:preview
Save
```
````
Enum values can be written the way you would in Razor. Event callbacks and `@bind` attributes are kept in the Code tab and skipped at render, so a realistic example does not break the page. The full rules are in [razor:preview](https://shelldocs.shellui.dev/docs/authoring/razor-preview.md).
## Examples with state
An example that needs a `@code` block can't be a fence. Write it as a `.razor` file in the docs project and show it with `DemoPreview`, which renders the component and uses the file as the source.
```csharp
o.RegisterComponentsFromAssembly("MyDocs.Components.Demos");
o.DemoSourceRoot = Path.Combine(builder.Environment.ContentRootPath, "Components", "Demos");
```
```markdown
` in markdown renders your library's `Card`. ShellDocs' primitive stays reachable under a `Docs` prefix:
| Name | Type | Default | Description |
|------|------|---------|-------------|
| `Card` | `your library` | | The tag resolves to the component you registered. |
| `DocsCard` | `ShellDocs` | | Always the built-in primitive. Every built-in has a Docs alias. |
A collision is logged at startup so you know it happened. If two of your own components claim one tag name, that is logged as a warning and the later registration wins.
When you document a library that shadows built-ins, use the `Docs` names for page furniture (`DocsCallout`, `DocsSteps`, `DocsTabs`) so the page keeps working whichever component the short name points to.
## Generic components
A generic component registers under its bare name and is closed per use with a type-parameter attribute:
```razor