Fixing the Server Explorer “The given key was not present in the dictionary” error

One of Visual Studio’s most cryptic error messages is Server Explorer’s infamous “the given key was not present in the dictionary.” This typically means that you’ve installed a custom data provider, created a Server Explorer connection using that provider, and then uninstalled the provider without deleting the Server Explorer entry.  This pretty much kills Server Explorer: from now on, any time you try to add or remove a connection, it barfs up the useless error.  This means you can’t even remove the dud connection.

The top Google hits for this issue recommend such brilliant solutions as creating a new user account and formatting your hard drive and reinstalling Windows.  Fortunately, you don’t have to go to such extreme lengths.

If you can guess what provider you might have installed and uninstalled, then you can reinstall that provider, delete all associated connections, then uninstall the provider once and for all.

If you can’t identify the provider, or can’t reinstall it, then you can go under the hood to remove the invalid connection.  Here’s how.

First, close all instances of Visual Studio.

Now, go into your user AppData directory (e.g. C:\Users\Alice\AppData) – note this may not be shown in Windows Explorer if you have “Show hidden files and folders” turned off – and drill down into Roaming > Microsoft > Visual Studio > 10.0 > ServerExplorer.  You’ll find a file in there called DefaultView.SEView.  This bad boy is where the connections are stored.

This is a plain XML file, so in theory, you can locate the dud connection by its Label and just remove the containing DataViewNode XML element.  In practice, I didn’t have much luck with this – the file stores blobs against connections by index, so deleting individual items can throw those indexes off.  But if you’ve got a lot of connections defined and you don’t want to have to recreate them, it’s probably worth giving this a try in case you get luckier than I did.

Otherwise, just delete the DefaultView.SEView file.

Then restart Visual Studio and party on.

Hat tip to Jason Short at VistaDB.