Change Project Namespace in Visual Studio

Instead of Find & Replace, you can right click the namespace in code and Refactor -> Rename.

Thanks to @Jimmy for this.

You can change the default namespace:
-> Project -> XXX Properties...
On Application tab: Default namespace

Other than that:
Ctrl-H
Find: WindowsFormsApplication16
Replace: MyName

Assuming this is for a C# project and assuming that you want to change the default namespace, you need to go to Project Properties, Application tab, and specify "Default Namespace".

Default namespace is the namespace that Visual studio sets when you create a new class. Next time you do Right Click > Add > Class it would use the namespace you specified in the above step.

"Default Namespace textbox in project properties is disabled" Same with me (VS 2010). I edited the project file ("xxx.csproj") and tweaked the item. That changed the default namespace.