I have a custom field type that I use in SharePoint 2013 lists. The custom field type is built using C# and JS and it extends the built-in SPFieldMultiLineText.
When I updated the RichTextMode property of the field in my code and redeployed that custom field type from Visual Studio to the SP server, the changes had no effect unless I remove the existing column that uses that custom field from each list and add it back, obviously losing all the data.
Is there any way that I can update the C# code behind the custom field, or particularly that property (SPFieldMultiLineText.RichTextMode), without having to remove the column and lose all data?
I have tried restarting the application pool and the whole server but that had no effect.
If that's relevant, the change I've made and want to apply is that I commented out this line in the constructor of the custom field type:
this.RichTextMode = SPRichTextMode.Compatible;