Gtk# in monodevelop not working anymore after upgrading to ubuntu 11.10 unity

Question

I had some monodevelop programs with a GTK# user interface running smoothly in ubuntu 11.04 without unity. I have upgraded to ubuntu 11.10 with unity. Now I get the following error:

"The type or namespace name 'Gtk' could not be found. Are you missing an assembly reference?".

And indeed in my references the references atk-sharp, gdk-sharp, glade-sharp, glid-sharp, stk-sharp and pango-sharp are colored red and I can't re-add them.

If I search in the software to install at gtk-sharp then it tells me Gtk# 2.10 is installed. If I start a new gtk project in monodevelop it gives the same errors.

Answer 1

This issue is due to Mono runtime version. Please change Mono runtime version of the project from Mono/.NET 3.5 to Mono/.NET 4.0 to fix this issue.

For this, please follow the steps as given below:

1. Launch 'Project Options' dialog using Solution Explorer.
2. Select 'General' project settings available under 'Build' group
3. Change Runtime version to Mono/.NET 4.0.
4. MonoDevelop will upgrade the current project as Visual Studio 2010 equivalents. Then, Rebuild the project and verify the outcome.

Answer 2

In my case solution was installing GTK# libraries. For Debian based distros GTK# could be installed as

sudo apt-get install gtk-sharp2

Or if you are using a RedHat based distro,

yum install gtk-sharp2-devel

See Tommy's comment above.