实体框架代码优先建模问题

Posted 2023-02-16

【中文标题】实体框架代码优先建模问题

【英文标题】：Entity framework code first modelling issues

【发布时间】：2021-09-01 01:37:11

【问题描述】：

当我尝试迁移/更新我的数据库时，我总是收到消息，例如此表和此表的此列会导致多个级联删除路径等。我了解级联删除路径是什么，但不知道为什么会出现错误在这种情况下，因为我在我的选择中做的一切都是正确的。

由于有多个模型相互连接，因此我为您提供了我的 github 存储库（文件夹后端/Messanger-Backend）的链接。

https://github.com/niklasxulls/ASP-Angular-Messanger

感谢您的帮助

编辑： 错误（我也尝试将第一个错误的原因注释掉，但是当第一个错误不再存在时，还会出现其他错误。这就是我发布 repos 的原因，所以你可以自己尝试）

PM> Add-Migration "Initial mig"
Build started...
Build succeeded.
To undo this action, use Remove-Migration.
PM> Update-Database
Build started...
Build succeeded.
fail: Microsoft.EntityFrameworkCore.Database.Command[20102]
      Failed executing DbCommand (7ms) [Parameters=[], CommandType='Text', CommandTimeout='30']
      CREATE TABLE [GroupMessageStatuses] (
          [GroupMessageStatusID] int NOT NULL IDENTITY,
          [GroupMessageID] int NOT NULL,
          [UserID] int NOT NULL,
          [MessageStatusID] int NOT NULL,
          [CreatedAt] datetime2 NULL,
          [UpdatedAt] datetime2 NULL,
          CONSTRAINT [PK_GroupMessageStatuses] PRIMARY KEY ([GroupMessageStatusID]),
          CONSTRAINT [FK_GroupMessageStatuses_GroupMessages_GroupMessageID] FOREIGN KEY ([GroupMessageID]) REFERENCES [GroupMessages] ([GroupMessageID]) ON DELETE CASCADE,
          CONSTRAINT [FK_GroupMessageStatuses_MessageStatuses_MessageStatusID] FOREIGN KEY ([MessageStatusID]) REFERENCES [MessageStatuses] ([MessageStatusID]) ON DELETE CASCADE,
          CONSTRAINT [FK_GroupMessageStatuses_Users_UserID] FOREIGN KEY ([UserID]) REFERENCES [Users] ([UserID]) ON DELETE CASCADE
      );
Failed executing DbCommand (7ms) [Parameters=[], CommandType='Text', CommandTimeout='30']
CREATE TABLE [GroupMessageStatuses] (
    [GroupMessageStatusID] int NOT NULL IDENTITY,
    [GroupMessageID] int NOT NULL,
    [UserID] int NOT NULL,
    [MessageStatusID] int NOT NULL,
    [CreatedAt] datetime2 NULL,
    [UpdatedAt] datetime2 NULL,
    CONSTRAINT [PK_GroupMessageStatuses] PRIMARY KEY ([GroupMessageStatusID]),
    CONSTRAINT [FK_GroupMessageStatuses_GroupMessages_GroupMessageID] FOREIGN KEY ([GroupMessageID]) REFERENCES [GroupMessages] ([GroupMessageID]) ON DELETE CASCADE,
    CONSTRAINT [FK_GroupMessageStatuses_MessageStatuses_MessageStatusID] FOREIGN KEY ([MessageStatusID]) REFERENCES [MessageStatuses] ([MessageStatusID]) ON DELETE CASCADE,
    CONSTRAINT [FK_GroupMessageStatuses_Users_UserID] FOREIGN KEY ([UserID]) REFERENCES [Users] ([UserID]) ON DELETE CASCADE
);
Microsoft.Data.SqlClient.SqlException (0x80131904): Das Einführen der FOREIGN KEY-Einschränkung "FK_GroupMessageStatuses_Users_UserID" für die GroupMessageStatuses-Tabelle kann Schleifen oder mehrere Kaskadepfade verursachen. Geben Sie ON DELETE NO ACTION oder ON UPDATE NO ACTION an, oder ändern Sie andere FOREIGN KEY-Einschränkungen.
Die Einschränkung oder der Index konnte nicht erstellt werden. Siehe vorherige Fehler.
   at Microsoft.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at Microsoft.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at Microsoft.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
   at Microsoft.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   at Microsoft.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean isAsync, Int32 timeout, Boolean asyncWrite)
   at Microsoft.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, Boolean sendToPipe, Int32 timeout, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry, String methodName)
   at Microsoft.Data.SqlClient.SqlCommand.ExecuteNonQuery()
   at Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteNonQuery(RelationalCommandParameterObject parameterObject)
   at Microsoft.EntityFrameworkCore.Migrations.MigrationCommand.ExecuteNonQuery(IRelationalConnection connection, IReadOnlyDictionary`2 parameterValues)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationCommandExecutor.ExecuteNonQuery(IEnumerable`1 migrationCommands, IRelationalConnection connection)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.Migrate(String targetMigration)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.UpdateDatabase(String targetMigration, String connectionString, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.UpdateDatabaseImpl(String targetMigration, String connectionString, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.UpdateDatabase.<>c__DisplayClass0_0.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
ClientConnectionId:86f8c011-ee35-44cd-a526-a5cfe9d579be
Error Number:1785,State:0,Class:16
Das Einführen der FOREIGN KEY-Einschränkung "FK_GroupMessageStatuses_Users_UserID" für die GroupMessageStatuses-Tabelle kann Schleifen oder mehrere Kaskadepfade verursachen. Geben Sie ON DELETE NO ACTION oder ON UPDATE NO ACTION an, oder ändern Sie andere FOREIGN KEY-Einschränkungen.
Die Einschränkung oder der Index konnte nicht erstellt werden. Siehe vorherige Fehler.

【问题讨论】：

能否提供原错误信息？

可能，你有 entity1 引用 entity2 和 entity2 也引用 entity1。

嗯，快速浏览一下，首先注意到GroupMessage 与UserMessage 有完全相同的问题，因此需要类似的解决方案。

但是GroupMessage和UserMessage的区别在于，UserMessage引用了2次User Model，而GroupMessage只引用了一次User和Group。

能否给我们您使用的表格并告诉我们这些表格之间的关系？您提供的链接找不到任何代码。

【参考方案1】：

我自己解决了这个问题。我不得不重新设置整个数据库，但现在它可以工作了。我有问题，比如双重关系。我还修复了 onDelete 问题，在 SQL Server 中创建了一个 ER 图，这让我更容易找到我的错误。