We always use Connection String in forms that we design but when you design a big software you should set the connection string for once and use it in many forms.
In this method you use the name of the Connection String instead of the connection string text.
Every time you want to change the connection string just change the main connection string in
the App.Config file.
By this method you don't need to change all of
the forms in your project, just change the Connection String in the App.Config.
Using the Code
First of all you should set the connection string in the App.Config file. For example I set the connection string for my database as you see
connectionString="Data Source=.;Initial Catalog=CharityManagement;Integrated Security=True"/>
After that you use the connection string in your forms using this code:
In your forms you set references that you want to use:
Then you can get the Connection String from the App.Config by using
You can use this method in both Windows Forms and ASP.NET projects.