Install libgtk2.0-cil by entering the following commands in the terminal:
sudo apt update sudo apt install libgtk2.0-cil
Description:
CLI binding for the GTK+ toolkit 2.12
This package provides the atk-sharp, gdk-sharp, gtk-dotnet, gtk-sharp and pango-sharp assemblies that allow CLI (.NET) programs to use the GTK+ user interface toolkit 2.12, ATK, Pango, GTK.NET and GDK. . GTK# 2.10 is a CLI (.NET) language binding for the GTK+ 2.10 toolkit . This package contains the GTK# assemblies
Homepage: http://www.mono-project.com/GtkSharp
Version: 2.12.40-2
Section: universe/libs