Which repository should I use for gtkcore

I am trying to build a cs file that uses Gtk. It gives compilation errors as it could not find Gtk package. When I tried to get GTK add-in, it fails with the message that it could not resolve the dependency on GTKCore and core. Which repository should I use to get these packages? I am using MintLinux (Daryna) that uses Ubuntu repositories for all the required updates. My MonoDevelop version is 0.14