> For the complete documentation index, see [llms.txt](https://docs.zongsoft.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.zongsoft.com/framework/core/components/identifier.md).

# 标识

从 Discussions 用户身份理解类型和值共同组成的标识。

Identifier 将标识类别与标识值放在一起，使通用安全组件不必依赖具体的论坛用户类。Discussions 的 UserIdentity 实现用户契约，将 UserId 转换为通用标识。

来源：[src/Security/UserIdentity.cs](https://github.com/Zongsoft/Zongsoft.Discussions/blob/main/src/Security/UserIdentity.cs#L102)（节选；上下文见源文件）。

{% code title="UserIdentity.cs" %}

```csharp
Identifier IIdentifiable.Identifier
{
	get => new(typeof(IUser), this.UserId);
	set => this.UserId = value.Validate<uint>(out var id) ? id : this.UserId;
}
#endregion
```

{% endcode %}

这里的类型是 IUser，而不是 UserIdentity。设置标识时先验证值能否作为 uint，再更新 UserId；不符合要求时保持原编号。标识用于回答对象是谁，不会自动加载用户资料或授予权限。

## 相关契约

| 类型             | 责任             |
| -------------- | -------------- |
| IIdentifiable  | 提供统一标识属性       |
| Identifier     | 保存类型、值及可选标签、描述 |
| Identifier\<T> | 值类型已确定的标识      |

UserIdentity 还包含 SiteId。用户编号和站点范围承担不同责任，跨模块传递 Identifier 后，业务操作仍需恢复或验证当前站点和资源权限。参见[认证与授权](/framework/security/authentication.md)。

框架定义：[Identifier](https://github.com/Zongsoft/framework/blob/main/Zongsoft.Core/src/Components/Identifier.cs)、[IIdentifiable](https://github.com/Zongsoft/framework/blob/main/Zongsoft.Core/src/Components/IIdentifiable.cs)。


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.zongsoft.com/framework/core/components/identifier.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.