Saving changes is not permitted. The changes you have made require the following tables to be dropped and re-created.You have either made changes to a table that can't be re-created or enabled the option Prevent saving changes that require the table to be re-created.

If you have getting above error, then you need to uncheck the Prevent saving changes that require the table to be re-creation text box in SQL Server Management Studio.

For this Goto
Tools->Options->Designers->Table and Database Designer 

Here uncheck the Prevent saving changes that require the table to be re-creation Check box and Save it :-).

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