# API/Controllers

In desktop applications it is common for controls such as Grids, Lists, Drop Downs, among many others to load a heavy amount of data, that in many cases is all displayed at once. In a web environment display controls are also common, but they don’t tend to load a heavy among of data at once, they rather invoke Web API Controllers to collect its data as needed.

WebMap also provides several Web API Controllers created to avoid sending big amount of data as part of the DTO/Mapper mechanism.

Controllers are responsible for responding to requests made from the front-end. In WebMAP, the items or nodes of any display control are not sent within the standard WebMAP request, so these kind of items and nodes are sent by means of a Controller Action.

```
[Route("api/treeview/FetchItems")]
[ApiController]
public class TreeViewController
{
    [HttpGet("{id}")]
    public Dictionary GetTreeViewItem(WebTreeView tv)
    {
        //...
    }
}
```

![](/files/jfTZ7jjp5i6Cp8S26Xhp)


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