I am trying to use MediaFileSelector in Kentico12 SP. But, it doesn't exist.

Hi there,

I am using the Kentico12 SP ( version : 12.0.29) and I read the document about MediaFileSelector in here

I tried to put MediaFileSelector in the widget properties like below.

[EditingComponent(MediaFileSelector.IDENTIFIER, Order = 2, Label = "Background image")]
public string BackgroundImage { get; set; }

But, I have an error like below

The name 'MediaFileSelector' does not exist in the current context

Can you tell me how to use this selector? or what am I supposed to do before using this?

Thank in advance, Luis