# GetExtension<T>()

> Gets optional extension object.

## Definition

* **Type:** Method
* **Namespace:** [UnityEditor.VersionControl](/engine/6000.5/script-reference/unityeditor/versioncontrol.md)
* **Assembly:** UnityEditor.CoreModule

```csharp
public virtual T GetExtension<T>() where T : class
```

### Returns

| Type | Description                                                                                                                                                           |
| ---- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| T    | Extension object if it's supported by [VersionControlObject](/engine/6000.5/script-reference/unityeditor/versioncontrol/versioncontrolobject.md). **null** otherwise. |

### Remarks

You can implement optional extensions in your [VersionControlObject](/engine/6000.5/script-reference/unityeditor/versioncontrol/versioncontrolobject.md)  to improve user experience. For example, the [IIconOverlayExtension](/engine/6000.5/script-reference/unityeditor/versioncontrol/iiconoverlayextension.md) enables you to draw VCS status overlays over asset icons. See the documentation for the full list of extensions. Future versions of Unity might add new extensions or stop calling existing ones.

The default GetExtension implementation attempts to cast [VersionControlObject](/engine/6000.5/script-reference/unityeditor/versioncontrol/versioncontrolobject.md) to extension type. This allows you to implement extensions directly in your [VersionControlObject](/engine/6000.5/script-reference/unityeditor/versioncontrol/versioncontrolobject.md) derived class.

```csharp
using UnityEditor.VersionControl;
using UnityEngine;

[VersionControl("Custom")]
public class CustomVersionControlObject : VersionControlObject, IIconOverlayExtension
{
    static Texture2D s_Icon;

    static Texture2D GetIcon()
    {
        if (s_Icon == null)
        {
            s_Icon = new Texture2D(8, 8);
            for (var y = 0; y < s_Icon.height; ++y)
            {
                for (var x = 0; x < s_Icon.width; ++x)
                {
                    var border = y == 0 || y == s_Icon.height - 1 || x == 0 || x == s_Icon.width - 1;
                    var color = border ? Color.white : Color.red;
                    s_Icon.SetPixel(x, y, color);
                }
            }
            s_Icon.Apply();
        }
        return s_Icon;
    }

    public void DrawOverlay(string assetPath, IconOverlayType type, Rect rect)
    {
        var topLeft = new Rect(rect.x, rect.y, 8, 8);
        var icon = GetIcon();
        GUI.DrawTexture(topLeft, icon);
    }
}
```

To support extensions implemented in separate classes you must overwrite this method and return an appropriate object.

```csharp
using UnityEditor.VersionControl;
using UnityEngine;

public class CustomIconOverlayExtension : IIconOverlayExtension
{
    public void DrawOverlay(string assetPath, IconOverlayType type, Rect rect)
    {
        var topLeft = new Rect(rect.x, rect.y, 8, 8);
        GUI.DrawTexture(topLeft, Texture2D.whiteTexture);
    }
}

[VersionControl("Custom")]
public class CustomVersionControlObject : VersionControlObject
{
    readonly IIconOverlayExtension m_IconOverlayExtension = new CustomIconOverlayExtension();

    public override T GetExtension<T>()
    {
        return m_IconOverlayExtension as T;
    }
}
```

Additional Resources: [VersionControlObject](/engine/6000.5/script-reference/unityeditor/versioncontrol/versioncontrolobject.md), [IIconOverlayExtension](/engine/6000.5/script-reference/unityeditor/versioncontrol/iiconoverlayextension.md), [IInspectorWindowExtension](/engine/6000.5/script-reference/unityeditor/versioncontrol/iinspectorwindowextension.md), [IPopupMenuExtension](/engine/6000.5/script-reference/unityeditor/versioncontrol/ipopupmenuextension.md), [ISettingsInspectorExtension](/engine/6000.5/script-reference/unityeditor/versioncontrol/isettingsinspectorextension.md).