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
Files to look at:
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
Files to look at:
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() .AddDefaultDashboardController(configurator => { configurator.SetDashboardStorage(new CustomDashboardStorage()); }); services.AddDevExpressControls(); } public class CustomDashboardStorage : IDashboardStorage { IEnumerable<DashboardInfo> IDashboardStorage.GetAvailableDashboardsInfo() { return new[] { new DashboardInfo { ID = "Dashboard", Name = "Dashboard" } }; } XDocument IDashboardStorage.LoadDashboard(string dashboardID) { throw new CustomException(); } void IDashboardStorage.SaveDashboard(string dashboardID, XDocument dashboard) { } }