How to make a default starting form

When you create a C# project by default Program.cs file will create.
In this file you can see this code.

Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Form1());

If you want to change the start up form from Form1 to Form2 then just change the third line.

Application.Run(new Form2());