---
source_files:
  - Common/DTS.CommonCore/Interface/DTS.Viewer/Legend/ILegendView.cs
  - Common/DTS.CommonCore/Interface/DTS.Viewer/Legend/ILegendViewModel.cs
generated_at: "2026-04-16T12:22:08.946405+00:00"
model: "zai-org/GLM-5-FP8"
schema_version: 1
sha256: "fa541836d2cec79b"
---

# Documentation: ILegendView / ILegendViewModel

## 1. Purpose

This module defines the core interfaces for a Legend component within a Viewer system, following the MVVM (Model-View-ViewModel) architectural pattern. `ILegendView` represents the view abstraction for legend visualization, while `ILegendViewModel` defines the contract for its corresponding ViewModel, establishing the relationship between the two layers. These interfaces enable decoupled communication between the legend's presentation logic and its UI rendering.

---

## 2. Public Interface

### `ILegendView`
**Namespace:** `DTS.Common.Interface`  
**Inherits:** `IBaseView`

A marker interface representing a legend view component. No members are defined beyond those inherited from `IBaseView`.

```csharp
public interface ILegendView : IBaseView { }
```

---

### `ILegendViewModel`
**Namespace:** `DTS.Common.Interface`  
**Inherits:** `IBaseViewModel`

Defines the contract for a legend ViewModel with access to its associated view.

| Member | Type | Access | Description |
|--------|------|--------|-------------|
| `View` | `ILegendView` | `get` | Returns the associated `ILegendView` instance for this ViewModel. |

```csharp
public interface ILegendViewModel : IBaseViewModel
{
    ILegendView View { get; }
}
```

---

## 3. Invariants

- `ILegendViewModel.View` must return a non-null `ILegendView` instance when accessed (implied by the contract, though nullability annotations are not present in the source).
- Both interfaces must maintain their inheritance from `IBaseView` and `IBaseViewModel` respectively, ensuring consistency with the broader view/viewmodel hierarchy.
- The `View` property on `ILegendViewModel` is read-only (getter only), suggesting the view association is established at construction or through internal mechanisms, not via public setters.

---

## 4. Dependencies

### This module depends on:
- `DTS.Common.Base` — Provides `IBaseView` and `IBaseViewModel` base interfaces from which these interfaces inherit.

### What depends on this module:
- **Cannot be determined from source alone.** Consumers would include concrete implementations of `ILegendView` and `ILegendViewModel`, as well as any components that render or interact with legend functionality.

---

## 5. Gotchas

- **Marker Interface:** `ILegendView` defines no members of its own. All functionality comes from `IBaseView`. Developers should consult `IBaseView` to understand available members.
- **Tight Coupling via Property:** The `ILegendViewModel.View` property creates a direct reference from the ViewModel to the View, which is a deviation from pure MVVM where ViewModels are typically view-agnostic. The rationale for this design choice is not documented in the source.
- **Missing Nullability Annotations:** The source lacks C# 8.0+ nullable reference type annotations, making it unclear whether `View` is guaranteed to be non-null.