How can I have 2 connection strings in Windows Forms

Question

I am building a Windows Form (WinForm) using Entity Framework 6, I should have 2 different connection strings.

1. a connection string for development mode.
   
2. a connection string for deployment.

how can I achieve that and easily switch between them?

I need this scenario to check if the Application is still in development mode (DEBUG), use the first connection string and if it is deployed, then use the second one.