The region and endregion directives control the display of collapsible regions in the code editor. These directives are ignored by the compiler. 

To mark code as a region, surround it with the region and endregion directives. You may include a message that will be displayed when the code is folded and hidden. 

The following code shows the use of a region in Delphi:

{$region 'Optional text that appears when the code block is folded'}
// code that can be hidden by folding
{$endregion}

The following code shows the use of a region in C#:

#region Optional text that appears when the code block is folded
// code that can be hidden by folding
#endregion