# System.ComponentModel.DataAnnotations

**Kind:** Service

**Source:** `Pams/Data/Pams.Data/Pams.Data.csproj` (line 1)

**Part of:** [Pams](subsystem-pams)

NuGet package dependency

`System.ComponentModel.DataAnnotations` is a NuGet package dependency declared by `Pams.Data.csproj`. It supports validation metadata on Pams.Data model properties, such as required fields, length constraints, and format rules, which .NET validation and model-binding code can evaluate.

## Diagram

```mermaid
sequenceDiagram
    participant Client
    participant API
    participant Model as Pams.Data Model
    participant Validation as System.ComponentModel.DataAnnotations

    Client->>API: Submit request payload
    API->>Model: Bind payload to model
    Model->>Validation: Evaluate validation attributes
    Validation-->>API: Validation results
    API-->>Client: Return success or validation errors
```

## Usage

```ts
type CreatePersonRequest = {
  name?: string;
  email?: string;
};

const request: CreatePersonRequest = {
  name: "Ada Lovelace",
  email: "ada@example.com",
};

const response = await fetch("/api/people", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
  },
  body: JSON.stringify(request),
});

if (!response.ok) {
  const errors = await response.json();
  console.error("Validation failed:", errors);
}
```

## AI Coding Instructions

- Keep validation attributes on Pams.Data model properties so validation rules remain close to the data contract.
- Match client request field names and types to the model properties decorated with data-annotation attributes.
- Handle validation-error responses in API clients instead of assuming all submitted payloads are accepted.
- Check `Pams.Data.csproj` before adding validation attributes to confirm the package reference remains available.

## Used by

1 reference from 1 file. Each is a place in this repository where the symbol is actually used — go read one rather than trusting an example.

### Injected or called by (1)

- `Pams.Data` — `Pams/Data/Pams.Data/Pams.Data.csproj`:1