Fedora ships with a very old version of mono: 2.10.8 compared to the upstream version of 3.12. Monodevelop is at version 2.8.8.4 while upstream is at 5.7.0 GTK# is at version 2.12 while upstream is at 3.14
Is this a duplicate of #1089426? By the way, there is now Mono 4.0.1 and MonoDevelop 5.9.0 as official releases on the Mono websites :)
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Fedora 23 comes with latest Mono 4 and MonoDevelop 5.9