The following example demostrates two approaches on how to handle errors in the ASP.NET Core Dashboard application:
- How to specify custom text for internal Dashboard errors
- How to throw a custom exception during a server-side processing and display the error in the Dashboard error toast
The dashboard in this project contains invalid data connection. This example shows how to override the default text in the exception that occurs when a controller tries to load data.
Implement the IExceptionFilter interface to create a custom exception filter and specify a custom exception message. The displayed text depends on whether the application is in development mode:
public class CustomExceptionFilter : IExceptionFilter { internal bool isDevelopmentMode = false; public CustomExceptionFilter(IWebHostEnvironment hostingEnvironment) { this.isDevelopmentMode = hostingEnvironment.IsDevelopment(); } string GetJson(string message) { return $"{{ \"Message\":\"{message}\" }}"; } public virtual void OnException(ExceptionContext context) { if(context.ExceptionHandled || context.Exception == null) { return; } context.Result = new ContentResult { Content = GetJson(!isDevelopmentMode ? "Custom exception text for end users" : "Custom exception text for developers"), ContentType = "application/json", StatusCode = (int)HttpStatusCode.BadRequest }; context.ExceptionHandled = true; } }Create a custom controller that uses the custom exception filter:
namespace AspNetCoreDashboard.ExceptionOnDataLoading.Controllers { [TypeFilter(typeof(CustomExceptionFilter))] public class CustomDashboardController : DashboardController { public CustomDashboardController(DashboardConfigurator configurator) : base(configurator) { } } }Specify the CustomDashboard controller when you configure endpoints:
public void Configure(IApplicationBuilder app, IWebHostEnvironment env) { // ... app.UseEndpoints(endpoints => { EndpointRouteBuilderExtension.MapDashboardRoute(endpoints, "api/dashboards", "CustomDashboard"); endpoints.MapControllerRoute( name: "default", pattern: "{controller=Home}/{action=Index}/{id?}" ); }); app.UseStaticFiles(); app.UseDevExpressControls(); }How to throw a custom exception during a server-side processing and display the error in the Dashboard error toast
This example shows how to throw a custom exception when a controller loads a dashboard.
Implement the IExceptionFilter interface to create a custom exception filter. The displayed text depends on whether the application is in development mode:
public class CustomExceptionFilter : IExceptionFilter { internal bool isDevelopmentMode = false; public CustomExceptionFilter(IWebHostEnvironment hostingEnvironment) { this.isDevelopmentMode = hostingEnvironment.IsDevelopment(); } string GetJson(string message) { return $"{{ \"Message\":\"{message}\" }}"; } public virtual void OnException(ExceptionContext context) { if(context.ExceptionHandled || context.Exception == null) { return; } CustomException customException = context.Exception as CustomException; string message = customException != null ? (isDevelopmentMode ? CustomException.UnsafeMessage : CustomException.SafeMessage) : ""; context.Result = new ContentResult { Content = GetJson(message), ContentType = "application/json", StatusCode = (int)HttpStatusCode.BadRequest }; context.ExceptionHandled = true; } }Create a custom controller that uses the custom exception filter:
namespace AspNetCoreDashboard.ExceptionOnLoadingDashboard.Controllers { [TypeFilter(typeof(CustomExceptionFilter))] public class CustomDashboardController : DashboardController { public CustomDashboardController(DashboardConfigurator configurator) : base(configurator) { } } }Specify the CustomDashboard controller when you configure endpoints:
public void Configure(IApplicationBuilder app, IWebHostEnvironment env) { // ... app.UseEndpoints(endpoints => { EndpointRouteBuilderExtension.MapDashboardRoute(endpoints, "api/dashboards", "CustomDashboard"); endpoints.MapControllerRoute( name: "default", pattern: "{controller=Home}/{action=Index}/{id?}" ); }); app.UseStaticFiles(); app.UseDevExpressControls(); }To throw an exception when the control loads a dashboard, create custom dashboard storage and override the LoadDashboard method:
public void ConfigureServices(IServiceCollection services) { services.AddMvc(); services.AddDevExpressControls(); services.AddScoped<DashboardConfigurator>((IServiceProvider serviceProvider) => { DashboardConfigurator configurator = new DashboardConfigurator(); configurator.SetDashboardStorage(new CustomDashboardStorage()); return configurator; }); } public class CustomDashboardStorage : IDashboardStorage { IEnumerable<DashboardInfo> IDashboardStorage.GetAvailableDashboardsInfo() { return new[] { new DashboardInfo { ID = "Dashboard", Name = "Dashboard" } }; } XDocument IDashboardStorage.LoadDashboard(string dashboardID) { // Custom Exception: throw new CustomException(); } void IDashboardStorage.SaveDashboard(string dashboardID, XDocument dashboard) { } }