Trying Mono on OS X - Getting "Error: Framework 'Mono / .NET 4.0' not installed."

Question

I have a pretty simple application that I wrote in Visual Studio 2010 in C# using .NET 4.0. All the form has on it is a couple of Buttons, Labels, a TreeView, a ComboBox and a TextBox.

I copied the project over to my install of OS X and opened the solution (VS2010) in MonoDevelop. It opens fine (although I don't know how to get the visual designer to show for Form1) - but when I go to run it I get the following error: Error: Framework 'Mono / .NET 4.0' not installed.

The issue is that I DO have the latest version of Mono installed, and it shows up properly (I think) in MonoDevelop. When I go to MonoDevelop->Preferences->.NET Runtimes it lists Mono 2.6.7 as the default.

So,

1. How do I get the visual designer to show for Form1.cs?

2. How do I get rid of the "Mono / .NET 4.0 not installed" error and get the project to compile and run?

3. All I did was copy the solution over to OS X and then opened it in MonoDevelop. Is there some conversion process the project needs to go through?

Thanks in advance!

Edit: I'd suppose I should give the specific version info. :)

OS X:        10.6.5 Snow Leopard
MonoDevelop: 2.4.2
Mono:        2.6.7 (shown in MonoDevelop in .NET Runtimes as 2.6.7 (Default))

I also started up a new project with a blank GTK form and was able to compile/run it.

Answer 1

Mono 2.6.7 doesn't provide a .net 4.0/C# 4 profile. You have to upgrade to at least Mono 2.8.