What are SharePoint Field Controls ?

In addition to Web Parts, pages in Microsoft SharePoint Server 2010 can contain field controls. Field controls are simple controls that you can create. They use a small amount of code to display the two modes of the controls: one for render time, and one for edit time.

Field controls are simple ASP.NET 2.0 server controls that provide the basic field functionality of SharePoint.

SharePoint Foundation and SharePoint Server 2010 provide several default field controls that you can use in your pages. All field controls that you use in a SharePoint Server 2010 site derive from a base class in SharePoint Foundation named FormComponent. You can extend any of the default SharePoint Foundation and SharePoint Server 2010 controls for your own specific functionality.

You can write a field control of your own by deriving from BaseRichField class, or you can write a field control that derives from the default field controls.