Close closes the form. The object still exists. You may need to use it again after calling the Close function to release the resource.
Dispose: destroys an object. The form object is recycled, that is, it does not exist. The resources released by the Dispose function are no longer used.
Application. exit. The entire program process ends. All objects in the project are destroyed and the entire application is exited.
Note: It may vary with MDI. In this case, you need to manually call Dispose to mark all controls of the form as garbage collection.
Close and Dispose call Exit to Exit a single form.
The Close call will cause the WM_CLOSE message. If you add a few lines of code in Form_Closing, you can block it. Set Handle to false.
Dispose directly releases the entire object, that is, manually releases it .. Net is an automatic garbage collection mechanism. If you do not release it, it can also be released by the system. Manual release is also beneficial.