JSONResult.SerializerSettings Must Be of Type System.Text.Json.JsonSerializerOptions

Environment

Product Version	14.0.20.219+
Product	Progress® Telerik® Reporting
.NET Framework	.NET Core 3.0+ / .NET 5+

Description

Starting with the Progress® Telerik® Reporting 2026 Q1 release, the .NET-based Reporting services now use System.Text.Json.

If you are using version 20.0.26.211 or newer, and encounter a similar exception, take a look at the JsonResult.SerializerSettings Must Be of Type Newtonsoft.Json.JsonSerializerSettings article instead.

If the Telerik Reporting REST Service project is targeting .NET Core 3.0+(or .NET 5+) and is throwing the error JSONResult.SerializerSettings Must Be of Type System.Text.Json.JsonSerializerOptions

Solution

1. Add the NuGet Package, Microsoft.AspNetCore.Mvc.NewtonsoftJson

2. Append .AddNewtonsoftJson() to any of the following services configurations:

   C#

   services.AddControllers().AddNewtonsoftJson();

   C#

   services.AddControllersWithViews().AddNewtonsoftJson();

   C#

   services.AddRazorPages().AddNewtonsoftJson();

See Also

• ASP.NET Core 3.0+ Telerik Reporting REST Service