"Scaffold" triggers for SQL Server

HasTrigger with trigger name only, to make the SQL Server SaveChanges work out of the box.

Closes #28185

src/EFCore.Design/Scaffolding/Internal/CSharpDbContextGenerator.cs

@@ -424,6 +424,43 @@ private void GenerateEntityType(IEntityType entityType)
                 GenerateManyToMany(skipNavigation);
             }
         }
+
+        var triggers = entityType.GetTriggers().ToArray();
+
+        if (triggers.Length > 0)
+        {
+            using (_builder.Indent())
+            {
+                _builder.AppendLine();
+
+                _builder.Append($"{EntityLambdaIdentifier}.{nameof(RelationalEntityTypeBuilderExtensions.ToTable)}(tb => ");
+
+                // Note: no trigger annotation support as of yet
+
+                if (triggers.Length == 1)
+                {
+                    var trigger = triggers[0];
+                    if (trigger.Name is not null)
+                    {
+                        _builder.AppendLine($"tb.HasTrigger({_code.Literal(trigger.Name)}));");
+                    }
+                }
+                else
+                {
+                    _builder.AppendLine("{");
+
+                    using (_builder.Indent())
+                    {
+                        foreach (var trigger in entityType.GetTriggers().Where(t => t.Name is not null))
+                        {
+                            _builder.AppendLine($"tb.HasTrigger({_code.Literal(trigger.Name!)});");
+                        }
+                    }
+
+                    _builder.AppendLine("});");
+                }
+            }
+        }
     }
 
     private void AppendMultiLineFluentApi(IEntityType entityType, IList<string> lines)

src/EFCore.Design/Scaffolding/Internal/RelationalScaffoldingModelFactory.cs

@@ -337,6 +337,16 @@ protected virtual ModelBuilder VisitTables(ModelBuilder modelBuilder, ICollectio
         VisitUniqueConstraints(builder, table.UniqueConstraints);
         VisitIndexes(builder, table.Indexes);
 
+        if (table.FindAnnotation(RelationalAnnotationNames.Triggers) is { Value: HashSet<string> triggers })
+        {
+            foreach (var triggerName in triggers)
+            {
+                builder.ToTable(table.Name, table.Schema, tb => tb.HasTrigger(triggerName));
+            }
+
+            table.RemoveAnnotation(RelationalAnnotationNames.Triggers);
+        }
+
         builder.Metadata.AddAnnotations(table.GetAnnotations());
 
         return builder;

src/EFCore.SqlServer/Scaffolding/Internal/SqlServerDatabaseModelFactory.cs

@@ -648,6 +648,7 @@ FROM [sys].[views] AS [v]
         GetColumns(connection, tables, filter, viewFilter, typeAliases, databaseCollation);
         GetIndexes(connection, tables, filter);
         GetForeignKeys(connection, tables, filter);
+        GetTriggers(connection, tables, filter);
 
         foreach (var table in tables)
         {
@@ -1295,6 +1296,48 @@ FROM [sys].[foreign_keys] AS [f]
         }
     }
 
+    private void GetTriggers(DbConnection connection, IReadOnlyList<DatabaseTable> tables, string tableFilter)
+    {
+        using var command = connection.CreateCommand();
+        command.CommandText = @"
+SELECT
+    SCHEMA_NAME([t].[schema_id]) AS [table_schema],
+    [t].[name] AS [table_name],
+    [tr].[name] AS [trigger_name]
+FROM [sys].[triggers] AS [tr]
+JOIN [sys].[tables] AS [t] ON [tr].[parent_id] = [t].[object_id]
+WHERE "
+            + tableFilter
+            + @"
+ORDER BY [table_schema], [table_name], [tr].[name]";
+
+        using var reader = command.ExecuteReader();
+        var tableGroups = reader.Cast<DbDataRecord>()
+            .GroupBy(
+                ddr => (tableSchema: ddr.GetValueOrDefault<string>("table_schema"),
+                    tableName: ddr.GetFieldValue<string>("table_name")));
+
+        foreach (var tableGroup in tableGroups)
+        {
+            var tableSchema = tableGroup.Key.tableSchema;
+            var tableName = tableGroup.Key.tableName;
+
+            var table = tables.Single(t => t.Schema == tableSchema && t.Name == tableName);
+
+            var triggers = new HashSet<string>();
+            table[RelationalAnnotationNames.Triggers] = triggers;
+
+            foreach (var triggerRecord in tableGroup)
+            {
+                var triggerName = triggerRecord.GetFieldValue<string>("trigger_name");
+
+                // We don't actually scaffold anything beyond the fact that there's a trigger with a given name.
+                // This is to modify the SaveChanges logic to not use OUTPUT without INTO, which is incompatible with triggers.
+                triggers.Add(triggerName);
+            }
+        }
+    }
+
     private bool SupportsTemporalTable()
         => _compatibilityLevel >= 130 && _engineEdition != 6;
 

test/EFCore.Design.Tests/Scaffolding/Internal/CSharpDbContextGeneratorTest.cs

@@ -1195,6 +1195,88 @@ protected override void OnModelCreating(ModelBuilder modelBuilder)
                                 // TODO
                             })).Message);
 
+        [ConditionalFact]
+        public void Trigger_works()
+            => Test(
+                modelBuilder => modelBuilder
+                    .Entity(
+                        "Employee",
+                        x =>
+                        {
+                            x.Property<int>("Id");
+                            x.ToTable(
+                                tb =>
+                                {
+                                    tb.HasTrigger("Trigger1");
+                                    tb.HasTrigger("Trigger2");
+                                });
+                        }),
+                new ModelCodeGenerationOptions { UseDataAnnotations = false },
+                code =>
+                {
+                    AssertFileContents(
+                        @"using System;
+using System.Collections.Generic;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata;
+
+namespace TestNamespace
+{
+    public partial class TestDbContext : DbContext
+    {
+        public TestDbContext()
+        {
+        }
+
+        public TestDbContext(DbContextOptions<TestDbContext> options)
+            : base(options)
+        {
+        }
+
+        public virtual DbSet<Employee> Employee { get; set; }
+
+        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
+        {
+            if (!optionsBuilder.IsConfigured)
+            {
+#warning "
+                        + DesignStrings.SensitiveInformationWarning
+                        + @"
+                optionsBuilder.UseSqlServer(""Initial Catalog=TestDatabase"");
+            }
+        }
+
+        protected override void OnModelCreating(ModelBuilder modelBuilder)
+        {
+            modelBuilder.Entity<Employee>(entity =>
+            {
+                entity.Property(e => e.Id).UseIdentityColumn();
+
+                entity.ToTable(tb => {
+                    tb.HasTrigger(""Trigger1"");
+                    tb.HasTrigger(""Trigger2"");
+                });
+            });
+
+            OnModelCreatingPartial(modelBuilder);
+        }
+
+        partial void OnModelCreatingPartial(ModelBuilder modelBuilder);
+    }
+}
+",
+                        code.ContextFile);
+                },
+                model =>
+                {
+                    var entityType = model.FindEntityType("TestNamespace.Employee")!;
+                    var triggers = entityType.GetTriggers();
+
+                    Assert.Collection(triggers.OrderBy(t => t.Name),
+                        t => Assert.Equal("Trigger1", t.Name),
+                        t => Assert.Equal("Trigger2", t.Name));
+                });
+
         protected override void AddModelServices(IServiceCollection services)
             => services.Replace(ServiceDescriptor.Singleton<IRelationalAnnotationProvider, TestModelAnnotationProvider>());