publicclassStartup
{
     .   .   .
// Configure dependencies for ReportDesignerController.
    services.TryAddSingleton<IReportDesignerServiceConfiguration>(sp => new ReportDesignerServiceConfiguration
    {
        DefinitionStorage = new MyFileDefStorage(
            Path.Combine(sp.GetService<IHostingEnvironment>().ContentRootPath, "..", "..", "..", "Report Designer", "Examples")),
        SettingsStorage = new FileSettingsStorage(
            Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "Telerik Reporting")),
    });
    
	. . . 
}


class MyFileDefStorage : FileDefinitionStorage
{
    public MyFileDefStorage(string baseDir) : base(baseDir)
    {
    }


    public override IEnumerable<string> ListDefinitions()
    {
        var reportPatterns = new string[] { "*.trdx", "*.trdp" };

 

        foreach (var pattern in reportPatterns)
        {
            var files = Directory.GetFiles(this.BaseDir, pattern, SearchOption.AllDirectories);
            foreach (var file in files)
            {
                var definitionId = file.Replace(this.BaseDir, string.Empty).TrimStart(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);
                yield return definitionId;
            }
        }
    }
}