> For the complete documentation index, see [llms.txt](https://docs.gapvelocity.ai/webmap/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.gapvelocity.ai/webmap/general/backend/faq/untitled-6.md).

# What is the ObservableAttribute?

The `ObservableAttribute` is an attribute defined in `Mobilize.WebMAP.Common.Attributes`. This attribute is defined in `Mobilize.WebMAP.Common` assembly.

## When is used this attribute? <a href="#when-is-used-this-attribute" id="when-is-used-this-attribute"></a>

This attribute is added before the declaration of a Class. And its intention is to mark this class as an observable class.

```
using Mobilize.WebMAP.Common.Attributes;

[Observable]
public class Class1
{
    .
    .
    .
}
```

## What happens to the class when used this attribute? <a href="#what-happens-to-the-class-when-used-this-attribute" id="what-happens-to-the-class-when-used-this-attribute"></a>

The weaver, when compiling the project that contains the observable class, will inject some behind generated code to the class that let WebMAP track the state of the declared instances of this class.