Show message to the user instead of bottom error line.

.gitignore

@@ -304,3 +304,4 @@ modules/virtual-file-explorer/app/Volo.Abp.VirtualFileExplorer.DemoApp/Logs/
 /templates/app/angular/package-lock.json
 /modules/client-simulation/demo/Volo.ClientSimulation.Demo/package-lock.json
 abp-build-config.json
+/templates/app/aspnet-core/src/MyCompanyName.MyProjectName.Blazor/Pages/Test/

framework/src/Volo.Abp.AspNetCore.Components.WebAssembly/Microsoft/Extensions/DependencyInjection/AbpWebAssemblyServiceCollectionExtensions.cs

@@ -0,0 +1,17 @@
+using System.Diagnostics.CodeAnalysis;
+using Microsoft.AspNetCore.Components.WebAssembly.Hosting;
+using Volo.Abp;
+
+namespace Microsoft.Extensions.DependencyInjection
+{
+    public static class AbpWebAssemblyServiceCollectionExtensions
+    {
+        public static WebAssemblyHostBuilder GetHostBuilder(
+            [NotNull] this IServiceCollection services)
+        {
+            Check.NotNull(services, nameof(services));
+
+            return services.GetSingletonInstance<WebAssemblyHostBuilder>();
+        }
+    }
+}

framework/src/Volo.Abp.AspNetCore.Components.WebAssembly/Volo/Abp/AspNetCore/Components/WebAssembly/AbpAspNetCoreComponentsWebAssemblyModule.cs

@@ -1,4 +1,6 @@
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using Volo.Abp.AspNetCore.Components.WebAssembly.ExceptionHandling;
 using Volo.Abp.AspNetCore.Mvc.Client;
 using Volo.Abp.Http.Client;
 using Volo.Abp.Modularity;
@@ -22,5 +24,12 @@ namespace Volo.Abp.AspNetCore.Components.WebAssembly
                 });
             });
         }
+
+        public override void ConfigureServices(ServiceConfigurationContext context)
+        {
+            context.Services
+                .GetHostBuilder().Logging
+                .AddProvider(new AbpExceptionHandlingLoggerProvider(context.Services));
+        }
     }
 }

framework/src/Volo.Abp.AspNetCore.Components.WebAssembly/Volo/Abp/AspNetCore/Components/WebAssembly/ExceptionHandling/AbpExceptionHandlingLogger.cs

@@ -0,0 +1,70 @@
+using System;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+
+namespace Volo.Abp.AspNetCore.Components.WebAssembly.ExceptionHandling
+{
+    public class AbpExceptionHandlingLogger : ILogger, IDisposable
+    {
+        private readonly IServiceCollection _serviceCollection;
+        private IServiceScope _serviceScope;
+        private IUiMessageService _messageService;
+
+        public AbpExceptionHandlingLogger(IServiceCollection serviceCollection)
+        {
+            _serviceCollection = serviceCollection;
+        }
+
+        public void Log<TState>(
+            LogLevel logLevel,
+            EventId eventId,
+            TState state,
+            Exception exception,
+            Func<TState, Exception, string> formatter)
+        {
+            if (logLevel != LogLevel.Critical && logLevel != LogLevel.Error)
+            {
+                return;
+            }
+
+            TryInitialize();
+
+            if (_messageService == null)
+            {
+                return;
+            }
+
+            //TODO: handle exception types
+            _messageService.ErrorAsync(
+                exception?.Message ?? state?.ToString() ?? "Unknown error!"
+            );
+        }
+
+        private void TryInitialize()
+        {
+            var serviceProvider = _serviceCollection.GetServiceProviderOrNull();
+            if (serviceProvider == null)
+            {
+                return;
+            }
+
+            _serviceScope = serviceProvider.CreateScope();
+            _messageService = _serviceScope.ServiceProvider.GetRequiredService<IUiMessageService>();
+        }
+
+        public bool IsEnabled(LogLevel logLevel)
+        {
+            return logLevel == LogLevel.Critical || logLevel == LogLevel.Error;
+        }
+
+        public IDisposable BeginScope<TState>(TState state)
+        {
+            return NullDisposable.Instance;
+        }
+
+        public void Dispose()
+        {
+            _serviceScope?.Dispose();
+        }
+    }
+}

framework/src/Volo.Abp.AspNetCore.Components.WebAssembly/Volo/Abp/AspNetCore/Components/WebAssembly/ExceptionHandling/AbpExceptionHandlingLoggerProvider.cs

@@ -0,0 +1,38 @@
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+
+namespace Volo.Abp.AspNetCore.Components.WebAssembly.ExceptionHandling
+{
+    public class AbpExceptionHandlingLoggerProvider : ILoggerProvider
+    {
+        private AbpExceptionHandlingLogger _logger;
+        private static readonly object SyncObj = new object();
+        private readonly IServiceCollection _serviceCollection;
+
+        public AbpExceptionHandlingLoggerProvider(IServiceCollection serviceCollection)
+        {
+            _serviceCollection = serviceCollection;
+        }
+
+        public ILogger CreateLogger(string categoryName)
+        {
+            if (_logger == null)
+            {
+                lock (SyncObj)
+                {
+                    if (_logger == null)
+                    {
+                        _logger = new AbpExceptionHandlingLogger(_serviceCollection);
+                    }
+                }
+            }
+
+            return _logger;
+        }
+
+        public void Dispose()
+        {
+            _logger.Dispose();
+        }
+    }
+}

framework/src/Volo.Abp.Core/Microsoft/Extensions/DependencyInjection/ServiceCollectionCommonExtensions.cs

@@ -24,7 +24,7 @@ namespace Microsoft.Extensions.DependencyInjection
                 .FirstOrDefault(d => d.ServiceType == typeof(T))
                 ?.ImplementationInstance;
         }
-        
+
         public static T GetSingletonInstance<T>(this IServiceCollection services)
         {
             var service = services.GetSingletonInstanceOrNull<T>();
@@ -165,5 +165,10 @@ namespace Microsoft.Extensions.DependencyInjection
         {
             return new Lazy<object>(() => services.GetRequiredService(type), true);
         }
+
+        public static IServiceProvider GetServiceProviderOrNull(this IServiceCollection services)
+        {
+	        return services.GetObjectOrNull<IServiceProvider>();
+        }
     }
-}
+}

templates/app/aspnet-core/src/MyCompanyName.MyProjectName.Blazor/wwwroot/index.html

@@ -19,11 +19,6 @@
 <body class="abp-application-layout bg-light">
     <app>Loading...</app>
 
-    <div id="blazor-error-ui">
-        An unhandled error has occurred.
-        <a href="" class="reload">Reload</a>
-        <a class="dismiss">🗙</a>
-    </div>
     <script src="_content/Microsoft.AspNetCore.Components.WebAssembly.Authentication/AuthenticationService.js"></script>
     <script src="_framework/blazor.webassembly.js"></script>