Symptoms

Trying to retrieve a SharePoint group users using a picker control, but receiving a "Invalid column name" error.
 

Diagnoses

In the picker control > Properties > Data Source, the user has selected all Filter Properties. However, the method the SmartObject is calling only returns 5 properties.
 

Resolution

1. Go to Program Files (x86)K2 blackpearlBin and run SmartObject Service Tester.exe

2. Locate the SharePoint SmartObject you have bound to your picker control and execute it. Remember to select the Get Users for Group method to execute.

3. In the results pane, you should notice that only the following properties are returned: User ID, User Login Name, User Email, User Title, Principal Type.

4. Return to K2 Designer, open the View and select the problematic picker control. Under the properties, configure data source, and make sure only the properties listed in point 3 are selected under the Filter Properties. Since the SmartObject and Get Users for Group method only returns 5 properties, selecting all the Filter Properties will cause the "Invalid column name" error.

5. You can try selecting one of the 5 Filter Properties I mentioned in point 3. If you are searching based on user's name, you can just select User Title. Try to avoid selecting all Filter Properties as it may have some performance impact, since the picker control is actually performing a search based on the filter properties you selected. More filter properties means longer search time.