FastColoredTextBox

Fast Colored TextBox is text editor component for .NET. Allows you to create custom text editor with syntax highlighting. It works well with small, medium, large and very-very large files.

It has such settings as foreground color, font style, background color which can be adjusted for arbitrarily selected text symbols. One can easily gain access to a text with the use of regular expressions. WordWrap, Find/Replace, Code folding and multilevel Undo/Redo are supported as well.

More details http://www.codeproject.com/Articles/161871/Fast-Colored-TextBox-for-syntax-highlighting

Nuget package https://www.nuget.org/packages/FCTB/