This book explains all about sharepoint.
Q. Whats New with SharePoint WebParts?
A developer can create two types of webparts using Visual Studio 2010.
1. Visual Webparts - Allows you to Drag and Drop the controls from the Toolbox to WebPart Design surface. You can of course write your custom code in the code file. You can also package and deploy your webparts directly to Sharepoint from VS by pressing Clt+F5. Visual studio 2010 also provides you with three different views for developing webparts. The views are split view, design view and Source view(as we have in designer 2007).
Note : The Visual Webpart project Item basically loads a User Control as a WebPart.
2. ASP.Net WebParts - Where a developer can build up User Interface and logic in a class file. You do not have designer for drag and drop of controls. This webpart inherits from standard ASP.Net webpart. For Deployment we can again use ctrl+f5 to deploy this webpart
Microsoft® Office SharePoint®
The Complete Reference
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