Add a New Line in a C# or Visual Basic TextBox
If you’re building a Windows Form Application, for example with C# or Visual Basic, then you may need to add a new line character, for example in a multiline TextBox. You do this using Enviroment.NewLine to insert the line break as follows:
My preferred use is with the += operator in C#:
This way, you can add extra lines of output to the TextBox as you require it.
References: Environment.NewLine on MSDN