Deployment conflicts were detected.

When developing solutions for SharePoint 2010 Visual Studio automatically resolves conflicts when redeploying a solution. By default, user will be prompted with the below message.

• If you select Resolve Automatically, your list and all of its data will be removed before a new instance of the list is provisioned. 
• To prevent this, you can set the Deployment Conflict Resolution property of the list instance in the Solution Explorer to None. 
• Simply right-click on the list instance project item in VS and select Properties. Then select None from the drop-down list of values: