Startup.cs

using System;
using DevExpress.AspNetCore;
using DevExpress.DashboardAspNetCore;
using DevExpress.DashboardCommon;
using DevExpress.DashboardWeb;
using DevExpress.DataAccess.Json;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.FileProviders;

namespace AspNetCoreDashboardBackend {
    public class Startup {
        // This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
        public Startup(IConfiguration configuration, IWebHostEnvironment hostingEnvironment) {
            Configuration = configuration;
            FileProvider = hostingEnvironment.ContentRootFileProvider;
        }

        public IConfiguration Configuration { get; }
        public IFileProvider FileProvider { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services) {
            // Configures services to use the Web Dashboard Control.
            services
                .AddEntityFrameworkSqlite()
                .AddDbContext<NorthwindContext>(options => options
                    .UseSqlite("Data Source=App_Data/nwind.db")
                );

            services
                .AddCors(options => {
                    options.AddPolicy("CorsPolicy", builder => {
                        builder.AllowAnyOrigin();
                        builder.AllowAnyMethod();
                        builder.WithHeaders("Content-Type");
                    });
                })
                .AddDevExpressControls()
                .AddControllersWithViews();

            services.AddScoped<DashboardConfigurator>((IServiceProvider serviceProvider) => {
                DashboardConfigurator configurator = new DashboardConfigurator();

                configurator.SetDashboardStorage(
                    new CustomDashboardStorage(FileProvider.GetFileInfo("App_Data/Dashboards").PhysicalPath,
                    serviceProvider.GetService<NorthwindContext>()));
                configurator.SetDataSourceStorage(CreateDataSourceStorage());
                configurator.SetConnectionStringsProvider(new DashboardConnectionStringsProvider(Configuration));
                configurator.ConfigureDataConnection += Configurator_ConfigureDataConnection;
                
                return configurator;
            });
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env) {
            // Registers the DevExpress middleware.
            app.UseDevExpressControls();
            app.UseRouting();
            app.UseCors("CorsPolicy");
            app.UseEndpoints(endpoints => {
                // Maps the default controller/action to display the service info view.
                endpoints.MapDefaultControllerRoute();
                // Maps the dashboard route.
                endpoints.MapDashboardRoute("api/dashboard", "DefaultDashboard");
                // Requires CORS policies.
                endpoints.MapControllers().RequireCors("CorsPolicy");
            });
        }
        

        public DataSourceInMemoryStorage CreateDataSourceStorage() {
            DataSourceInMemoryStorage dataSourceStorage = new DataSourceInMemoryStorage();
                        
            DashboardJsonDataSource jsonDataSourceSupport = new DashboardJsonDataSource("Support");
            jsonDataSourceSupport.ConnectionName = "jsonSupport";
            jsonDataSourceSupport.RootElement = "Employee";
            dataSourceStorage.RegisterDataSource("jsonDataSourceSupport", jsonDataSourceSupport.SaveToXml());

            return dataSourceStorage;
        }

        private void Configurator_ConfigureDataConnection(object sender, ConfigureDataConnectionWebEventArgs e) {
            if (e.ConnectionName == "jsonSupport") {
                Uri fileUri = new Uri(FileProvider.GetFileInfo("App_Data/Support.json").PhysicalPath, UriKind.RelativeOrAbsolute);
                JsonSourceConnectionParameters jsonParams = new JsonSourceConnectionParameters();
                jsonParams.JsonSource = new UriJsonSource(fileUri);
                e.ConnectionParameters = jsonParams;
            }
        }
    }
}