crawl space of programming

Some application cannot be run in multiple instance for several reasons. So you need to avoid a second instance will run, but how? You cannot directly block the execution of your application, so you need to take care of the problem in your code.

Sometimes you need to loop cells in Excel. In fact it is looping rows and columns, because cells have two dimensions. The rows are counted up, but the columns are named alphabetic. Looping them is not that easy and gets harder until you hit the Z , because the next 'letter' would be AA . So a number would be more easy.

If you are using an asp:hyperlink to another page in your provider hosted app you will see the SharePointContextProvider will not be able to handle the redirect. To fix the problem you need to add a click event and call a redirect in your code behind.