How it was constructed

FancyTextBox draws background text in the edit box window on paint requests as necessary.
FancyTextBox was designed as a container control using custom ParentControlDesigner called FancyTextBoxDesigner. This allowed for controls to be dropped on FancyTextBox at design time.  FancyTextBoxDesigner class is defined inside FancyTextBox class as internal class which hides designer from public view and at the same time allows it to use private properties and methods of FancyTextBox class.

Controls can be added to FancyTextBox programmatically by simply using FancyTextBox.Controls.Add(control) method. When control is added it's Left property needs to be set to 0 to insert on the left side or to FancyTextBox.Width to insert it on the right side.

FancyTextBox adjusts internal edit box margins within which text is written to accommodate controls that are added on left and right of control.

Difficulties encountered

ParentControlDesigner DragDrop event does not return the control that is being dropped in eventargs which makes it impossible to reset dropped control's location for it show in the correct position inside FancyTextBox. After much investigation and experimenting I noticed that CanParent method of ParentControlDesigner fires before OnDragDrop. So I simply overrode CanParent method to save control in private variable to be used in OnDragDrop.

The ambient properties, such as Font, Cursor, Background Color etc., of controls that are added to FancyTextBox default to FancyTextBox values unless they are explicitely overriden. I didn't find a workaround this issue as of yet.

Right-To-Left was not implemented here.

DateBox Custom Control

DateBox control is suitable for entering a general date. It was created using FancyTextBox and MonthCalendar control which acts as a dropdown to assist in date selection.