Fixing a Sneaky JSON Casing Bug when Exporting in Optimizely CMS

*Note: This issue seems to be resolved with EPiServer.CMS Version 12.33.1.

We recently encountered a pretty frustrating issue while working with Optimizely CMS: after attempting to upgrade to the latest NuGet packages, data exports would just hang—no error, no download, just… spinning forever.

We contacted support, and they had us rule out a timeout problem by tweaking timeout settings in appsettings.json. No luck.
Eventually, after providing Optimizely Support access to a lower environment, they discovered something weird in the export polling response: the JSON was being returned in PascalCase instead of camelCase. Here’s what the problematic JSON looked like:

{
  "FileId": "tmpOMsqJV.tmp",
  "IsDone": true,
  "IsAborting": false,
  "IsTest": false,
  "ErrorMessages": [],
  "WarningMessages": [],
  "InfoMessages": ["Export completed without errors or warnings"],
  "PageCount": 44,
  ...
}

The client-side JavaScript was expecting camelCase (isDone, not IsDone), so even though the export finished, the UI didn’t recognize it. The result? An endless spinner.
After some digging, we found this in our Startup.cs:

services.AddControllers(
    options => options.SuppressImplicitRequiredAttributeForNonNullableReferenceTypes = true)
    .AddJsonOptions(opts => opts.JsonSerializerOptions.PropertyNamingPolicy = null);

Setting PropertyNamingPolicy to null meant the JSON output kept the C# property casing (PascalCase). Changing that to use JsonNamingPolicy.CamelCase solved the problem:

services.AddControllers(
    options => options.SuppressImplicitRequiredAttributeForNonNullableReferenceTypes = true)
    .AddJsonOptions(opts => opts.JsonSerializerOptions.PropertyNamingPolicy = JsonNamingPolicy.CamelCase);

Once that was in place, the export started working correctly. Of course, we're planning more testing to make sure this doesn't cause side effects elsewhere, but if you run into mysterious export issues after a NuGet update or configuration change—double-check your JSON naming settings. It might just save you hours of Googling.