EF6 AssociationType多对多表上的System.InvalidOperationException

Question

我正在使用EF6迁移代码优先约定来重命名我的所有表，属性，模式等，以适合我们的内部数据库约定。 公约正确地重命名了所有的字段和表名称，按预期进行编译和脚手架。 但是，当我更新数据库时，出现以下错误：

System.InvalidOperationException: Sequence contains no matching element
   at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source, Func`2 predicate)
   at System.Data.Entity.Migrations.DbMigrator.FillInForeignKeyOperations(IEnumerable`1 operations, XDocument targetModel)
   at System.Data.Entity.Migrations.DbMigrator.ExecuteOperations(String migrationId, VersionedModel targetModel, IEnumerable`1 operations, IEnumerable`1 systemOperations, Boolean downgrading, Boolean auto)
   at System.Data.Entity.Migrations.DbMigrator.ApplyMigration(DbMigration migration, DbMigration lastMigration)
   at System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.ApplyMigration(DbMigration migration, DbMigration lastMigration)
   at System.Data.Entity.Migrations.DbMigrator.Upgrade(IEnumerable`1 pendingMigrations, String targetMigrationId, String lastMigrationId)
   at System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.Upgrade(IEnumerable`1 pendingMigrations, String targetMigrationId, String lastMigrationId)
   at System.Data.Entity.Migrations.DbMigrator.UpdateInternal(String targetMigration)
   at System.Data.Entity.Migrations.DbMigrator.<>c__DisplayClassc.<Update>b__b()
   at System.Data.Entity.Migrations.DbMigrator.EnsureDatabaseExists(Action mustSucceedToKeepDatabase)
   at System.Data.Entity.Migrations.Infrastructure.MigratorBase.EnsureDatabaseExists(Action mustSucceedToKeepDatabase)
   at System.Data.Entity.Migrations.DbMigrator.Update(String targetMigration)
   at System.Data.Entity.Migrations.Infrastructure.MigratorBase.Update(String targetMigration)
   at System.Data.Entity.Migrations.Design.ToolingFacade.UpdateRunner.Run()
   at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
   at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
   at System.Data.Entity.Migrations.Design.ToolingFacade.Run(BaseRunner runner)
   at System.Data.Entity.Migrations.Design.ToolingFacade.Update(String targetMigration, Boolean force)
   at System.Data.Entity.Migrations.UpdateDatabaseCommand.<>c__DisplayClass2.<.ctor>b__0()
   at System.Data.Entity.Migrations.MigrationsDomainCommand.Execute(Action command)
Sequence contains no matching element

这是导致此问题的表的迁移代码。 我已经验证PK正确，外键表存在并且类型正确，索引指向正确的字段等。在这里，我全都没有想法。

CreateTable(
            "cw.map_cw_service_cw_immunization",
            c => new
                {
                    cw_service_id = c.String(nullable: false, maxLength: 36),
                    cw_immunization_id = c.String(nullable: false, maxLength: 36),
                })
            .PrimaryKey(t => new { t.cw_service_id, t.cw_immunization_id })
            .ForeignKey("cw.careware_services", t => t.cw_service_id, cascadeDelete: true)
            .ForeignKey("cw.careware_immunizations", t => t.cw_immunization_id, cascadeDelete: true)
            .Index(t => t.cw_service_id, name: "IX_CarewareService_Id")
            .Index(t => t.cw_immunization_id, name: "IX_CarewareImmunization_Id");

    }

更新：我已将问题缩小为外键问题。 如果我注释掉这两种外键扩展方法，数据库将按预期更新。 但是，显然这不是一个有效的解决方法，因为该表现在没有FK约束。

Answer 1

我根据错误堆栈进行了一些挖掘，并在EntityFramework源代码中找到了以下方法。 该错误是由Single（）未返回值引起的。 只有一个.Single（）操作不会返回默认值，因此显然是罪魁祸首。 该操作返回与EntitySetName匹配的单个EntityTypeElement（因为它们应该是唯一的）。 长话短说，我意识到我必须在代码的某个地方意外地更改EntitySet.Name值而不是EntitySet.Table值。 瞧，那是罪魁祸首。 我更改了代码行，并且效果很好。

TL; DR; -始终检查以确保您正在设置EntitySet.Table值，并且在更改时未更改EntitySet.Name值。

private void FillInForeignKeyOperations(IEnumerable<MigrationOperation> operations, XDocument targetModel)
{
    DebugCheck.NotNull(operations);
    DebugCheck.NotNull(targetModel);

    foreach (var foreignKeyOperation
        in operations.OfType<AddForeignKeyOperation>()
                     .Where(fk => fk.PrincipalTable != null && !fk.PrincipalColumns.Any()))
    {
        var principalTable = GetStandardizedTableName(foreignKeyOperation.PrincipalTable);
        var entitySetName
            = (from es in targetModel.Descendants(EdmXNames.Ssdl.EntitySetNames)
               where _modelDiffer.GetQualifiedTableName(es.TableAttribute(), es.SchemaAttribute())
                                 .EqualsIgnoreCase(principalTable)
               select es.NameAttribute()).SingleOrDefault();

        if (entitySetName != null) //ERROR SOURCE IS BELOW
        {
            var entityTypeElement
                = targetModel.Descendants(EdmXNames.Ssdl.EntityTypeNames)
                             .Single(et => et.NameAttribute().EqualsIgnoreCase(entitySetName)); 

            entityTypeElement
                .Descendants(EdmXNames.Ssdl.PropertyRefNames).Each(
                    pr => foreignKeyOperation.PrincipalColumns.Add(pr.NameAttribute()));
        }
        else
        {
            // try and find the table in the current list of ops
            var table
                = operations
                    .OfType<CreateTableOperation>()
                    .SingleOrDefault(ct => GetStandardizedTableName(ct.Name).EqualsIgnoreCase(principalTable));

            if ((table != null)
                && (table.PrimaryKey != null))
            {
                table.PrimaryKey.Columns.Each(c => foreignKeyOperation.PrincipalColumns.Add(c));
            }
            else
            {
                throw Error.PartialFkOperation(
                    foreignKeyOperation.DependentTable, foreignKeyOperation.DependentColumns.Join());
            }
        }
    }
}