Fix broken build

Returned accidentally removed StartupConfiguratiionExtensions file
and removed what supposed to be removed ApplicationBuilderExtensions,
plus resolved warning happened after merge of one of PRs

Author: alex-kulakov

Extensions/Xtensive.Orm.Web/ApplicationBuilderExtensions.cs

@@ -0,0 +1,54 @@
+// Copyright (C) 2021 Xtensive LLC.
+// This code is distributed under MIT license terms.
+// See the License.txt file in the project root for more information.
+
+using System;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.AspNetCore.Mvc.Filters;
+using Xtensive.Orm.Web.Filters;
+using Xtensive.Orm.Web.Middleware;
+
+namespace Xtensive.Orm.Web
+{
+  /// <summary>
+  /// Contains extensions which are used in Startup.cs to configure application
+  /// </summary>
+  public static class StartupConfigurationExtensions
+  {
+    /// <summary>
+    /// Adds <see cref="OpenSessionMiddleware"/> to ASP.NET Core middleware pipeline.
+    /// </summary>
+    /// <param name="builder"><see cref="IApplicationBuilder"/> instance.</param>
+    /// <returns><paramref name="builder"/> with <see cref="OpenSessionMiddleware"/>.</returns>
+    public static IApplicationBuilder UseDataObjectsSessionOpener(this IApplicationBuilder builder) =>
+      builder.UseMiddleware<OpenSessionMiddleware>();
+
+    /// <summary>
+    /// Registers a <see cref="SessionAccessor"/> as scoped service to be able to
+    /// have access to session/transaction as parameter in either MVC controllers' actions or
+    /// constuctors, and in Razor Pages.
+    /// </summary>
+    /// <param name="services">A service collection to add <see cref="SessionAccessor"/>.</param>
+    /// <returns>The same collection instance with registered accessor.</returns>
+    public static IServiceCollection AddDataObjectsSessionAccessor(this IServiceCollection services) =>
+      services.AddScoped<SessionAccessor>();
+
+    /// <summary>
+    /// Adds <see cref="SessionActionFilter"/> to action filters.
+    /// </summary>
+    /// <param name="filters">The filter collection to add the filter.</param>
+    /// <returns>A <see cref="IFilterMetadata"/> representing added filter.</returns>
+    public static IFilterMetadata AddDataObjectsSessionActionFilter(this FilterCollection filters) =>
+      AddDataObjectsSessionActionFilter(filters, 0);
+
+    /// <summary>
+    /// Adds <see cref="SessionActionFilter"/> to action filters.
+    /// </summary>
+    /// <param name="filters">The filter collection to add the filter.</param>
+    /// <param name="order">The order of the added filter.</param>
+    /// <returns>A <see cref="IFilterMetadata"/> representing added filter.</returns>
+    public static IFilterMetadata AddDataObjectsSessionActionFilter(this FilterCollection filters, int order) =>
+      filters.Add(typeof(SessionActionFilter), order);
+  }
+}

Extensions/Xtensive.Orm.Web/StartupConfigurationExtensions.cs

@@ -56,8 +56,8 @@ public class EventInfo : SessionBound, IDisposable
     public EntityFieldValueEventArgs EntityFieldValueSettingArgs;
     public EntityFieldValueSetEventArgs EntityFieldValueSetArgs;
 
-    public QueryEventArgs? QueryExecuting;
-    public QueryEventArgs? QueryExecuted;
+    public QueryEventArgs QueryExecuting;
+    public QueryEventArgs QueryExecuted;
 
     public DbCommandEventArgs? DbCommandExecuting;
     public DbCommandEventArgs? DbCommandExecuted;