ReportSource reportSource = _resolver.Resolve(reportName, OperationOrigin.GenerateReportDocument, resolvedParams);
var processor = new ReportProcessor();
var deviceInfo = new System.Collections.Hashtable();
RenderingResult result = processor.RenderReport("PDF", reportSource, deviceInfo);

"telerikReporting": {
    "processing": {
      "sharedDataSourceResolver": {
        "provider": "custom",        
        "parameters": [
          {
            "name": "typeName",
            "value": "NameSpaceAndClassName, containing AssemblyName"
          }
        ]
      }
    } 
  }

builder.Services.AddScoped<IReportServiceConfiguration>(sp =>
{
    return new ReportServiceConfiguration
    {
        // ReportingEngineConfiguration = sp.GetService<IConfiguration>(), //(?? is this needed? does not load config either
       Storage = new FileStorage(),
       ReportSourceResolver = sp.GetRequiredService<DatabaseReportSourceResolver>()
    };
});

builder.Services.AddScoped<ISharedDataSourceStorage, DatabaseSharedDataSourceStorage>();
builder.Services.AddScoped<IReportDesignerServiceConfiguration>(sp => new ReportDesignerServiceConfiguration
{
    DefinitionStorage = new DatabaseDefinitionStorage(sp.GetRequiredService<IReportDefinitionDataStore>()),  
    SharedDataSourceStorage = sp.GetRequiredService<ISharedDataSourceStorage>(),
    SettingsStorage = new FileSettingsStorage(System.IO.Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "Telerik Reporting")),
});

Uncaught (in promise) RangeError: Maximum call stack size exceeded
    at init.wrap (webReportDesigner.kendo-19.3.25.1111.min.js:16:433731)
    at webReportDesigner.kendo-19.3.25.1111.min.js:16:432594
    at Array.forEach (<anonymous>)

export const ReportDesigner = (): React.ReactElement => {
    const initializedRef = React.useRef(false)
    useEffect(() => {
        if (initializedRef.current) return
        // Make jQuery global for legacy scripts
        //@ts-expect-error: TS2339 (TS) Property '$' does not exist on type 'Window & typeof globalThis'.
        window.$ = window.$ || $
        //@ts-expect-error: TS2339 (TS) Property 'jQuery' does not exist on type 'Window & typeof globalThis'.
        window.jQuery = window.jQuery || $
        // Ensure Kendo exists globally
        const kendo = window.kendo
        if (!kendo) {
            console.error("Kendo UI must be loaded globally before initializing the designer!")
            return
        }
        
        const initDesigner = () => {
            if ($("#reportDesigner").data("telerik_WebReportDesigner")) {
                return // already initialized
            }
            //@ts-expect-error: TS2339 because Property 'telerik_WebReportDesigner' does not exist on type 'JQuery<HTMLElement>'.
            ($("#reportDesigner")).telerik_WebReportDesigner({
                serviceUrl: "/api/ReportDesigner",
            })
        }
        // Load Telerik designer scripts sequentially
        const loadDesignerScripts = (): Promise<void> => {
            return new Promise((resolve, reject) => {
                if (document.querySelector('script[src*="webReportDesigner-19.3"]')) {
                    resolve()
                    return
                }
                const coreScript = document.createElement("script")
                coreScript.src = "/telerik/webReportDesigner-19.3.25.1111.js"
                coreScript.onload = () => {
                    const kendoScript = document.createElement("script")
                    kendoScript.src = "/telerik/webReportDesigner.kendo-19.3.25.1111.min.js"
                    kendoScript.onload = () => {
                        // Plugin should now exist
                        //@ts-expect-error: TS2339 (TS) Property 'telerik_WebReportDesigner' does not exist on type 'JQuery<HTMLElement>'.
                        if (!$.fn.telerik_WebReportDesigner) {
                            console.error("Telerik Web Report Designer plugin not loaded!")
                            reject(new Error("Telerik plugin not loaded"))
                            return
                        }
                        resolve()
                    }
                    kendoScript.onerror = (error) => reject(new Error(`Failed to load kendo integration script ${error}`))
                    document.body.appendChild(kendoScript)
                }
                coreScript.onerror = (error) => reject(new Error(`Failed to load core designer script ${error}`))
                document.body.appendChild(coreScript)
            })
        }
        // Ensure scripts loaded + token ready
        loadDesignerScripts().then(() => initDesigner()).catch(err => console.error(err))
    }, [])

    return <div id="reportDesigner" style={{ height: "900px" }} />
}

    public class CustomSharedDataSourceResolver : Telerik.Reporting.Processing.Data.ISharedDataSourceResolver
    {
        /// <summary>
        /// Resolves and returns a DataSource instance from the provided <paramref name="sharedDataSourcePath"/> parameter.
        /// </summary>
        /// <param name="sharedDataSourcePath">The value of the Path property obtained from the report definition. Might be relative or absolute.</param>
        /// <returns></returns>
        public DataSource Resolve(string sharedDataSourcePath)
        {
            ValidateConfiguration();

            var absolutePathToSharedDataSourceDefinition =
                GetExistingFilePath(Configuration.Instance.ReportsPath, sharedDataSourcePath)
                ?? GetExistingFilePath(Configuration.Instance.SharedDataSourcesPath, sharedDataSourcePath);

[...]

{
  "ConnectionStrings": {[...]},
  "AllowedHosts": "*",
  "AzureStorageBlobConfig": {[...]},
  "Logging": {[...]},
  "TelerikReporting": {
    "Processing": {
      "SharedDataSourceResolver": {
        "Provider": "custom",
        "Parameters": [
          {
            "Name": "typename",
            "Value": "TgsFlow.Plugin.Reporting.TelerikReporting.Utilities.CustomSharedDataSourceResolver, TgsFlow.Plugin.Reporting.TelerikReporting"
          }
        ]
      }
    }
  }
}