不能在交易中使用 DbContext.Query

Question

我正在使用 EF6 查询后端数据库。用户可以自定义一个临时table并从临时table中查询数据。我正在使用

DataTable result = context.Query(queryStatement);

得到结果，它一直运行良好。

现在需要在一系列其他 sql 命令中进行查询，并且需要一个事务。所以我有

public static DataTable GetData()
{
    using (MyDbContext context = new MyDbContext())
    using (DbContextTransaction tran = context.Database.BeginTransaction())
    {
        try
        {
            int rowAffected = context.Database.ExecuteSqlCommand(
                "UPDATE [MyDb].dbo.[TableLocks] SET RefCount = RefCount + 1 WHERE TableName = 'TESTTABLE1'");
            if (rowAffected != 1)
                throw new Exception("Cannot find 'TestTable1'");

            //The following line will raise an exception
            DataTable result = context.Query("SELECT TOP 100 * FROM [MyDb].dbo.[TestTable1]");
            //This line will work if I change it to 
            //context.Database.ExecuteSqlCommand("SELECT TOP 100 * FROM [MyDb].dbo.[TestTable1]");
            //but I don't know how to get the result out of it.
            context.Database.ExecuteSqlCommand(
                "UPDATE [MyDb].dbo.[TableLocks] SET RefCount = RefCount - 1 WHERE TableName = 'TestTable1'");
            tran.Commit();

            return result;
        }
        catch (Exception ex)
        {
            tran.Rollback();
            throw (ex);
        }
    }
}

但这在执行时抛出异常context.Query

ExecuteReader requires the command to have a transaction when the connection 
assigned to the command is in a pending local transaction.  The Transaction 
property of the command has not been initialized.

当我阅读这篇文章时：https://docs.microsoft.com/en-us/ef/ef6/saving/transactions 它说：

Entity Framework does not wrap queries in a transaction.

是这个问题的原因吗？

如何在交易中使用 context.Query()？

我还能用什么？

我尝试了所有其他方法，none 有效 - 因为无法事先预测 return 数据类型。

我才发现，Query方法是在MyDbContext中定义的！

    public DataTable Query(string sqlQuery)
    {
        DbProviderFactory dbFactory = DbProviderFactories.GetFactory(Database.Connection);

        using (var cmd = dbFactory.CreateCommand())
        {
            cmd.Connection = Database.Connection;
            cmd.CommandType = CommandType.Text;
            cmd.CommandText = sqlQuery;
            using (DbDataAdapter adapter = dbFactory.CreateDataAdapter())
            {
                adapter.SelectCommand = cmd;

                DataTable dt = new DataTable();
                adapter.Fill(dt);

                return dt;
            }
        }
    }

Answer 1

可能是您遗漏了这一部分 -

you are free to execute database operations either directly on the SqlConnection itself, or on the DbContext. All such operations are executed within one transaction. You take responsibility for committing or rolling back the transaction and for calling Dispose() on it, as well as for closing and disposing the database connection

然后是这个代码库 -

using (var conn = new SqlConnection("..."))
{
    conn.Open();

    using (var sqlTxn = 
    conn.BeginTransaction(System.Data.IsolationLevel.Snapshot))
    {
        try
        {
            var sqlCommand = new SqlCommand();
            sqlCommand.Connection = conn;
            sqlCommand.Transaction = sqlTxn;
            sqlCommand.CommandText =
                       @"UPDATE Blogs SET Rating = 5" +
                        " WHERE Name LIKE '%Entity Framework%'";
            sqlCommand.ExecuteNonQuery();

            using (var context =  
                new BloggingContext(conn, contextOwnsConnection: false))
            {
                        context.Database.UseTransaction(sqlTxn);

                        var query =  context.Posts.Where(p => p.Blog.Rating >= 5);
                        foreach (var post in query)
                        {
                            post.Title += "[Cool Blog]";
                        }
                       context.SaveChanges();
                    }

                    sqlTxn.Commit();
        }
        catch (Exception)
        {
             sqlTxn.Rollback();
        }
    }
}

特别是这个 -

context.Database.UseTransaction(sqlTxn);

Answer 2

抱歉各位，如上所述，我以为 Query 方法来自 EF，但我检查了代码，发现 它实际上是由另一个开发人员编写的，定义在 class MyDbContext 中。 因为这个 class 是由 EF 生成的，我从来没有想过有人添加了方法。

是

public DataTable Query(string sqlQuery)
{
    DbProviderFactory dbFactory = DbProviderFactories.GetFactory(Database.Connection);

    using (var cmd = dbFactory.CreateCommand())
    {
        cmd.Connection = Database.Connection;
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = sqlQuery;

        //And I added this line, then problem solved.
        if (Database.CurrentTransaction != null)
            cmd.Transaction = Database.CurrentTransaction.UnderlyingTransaction;

        using (DbDataAdapter adapter = dbFactory.CreateDataAdapter())
        {
            adapter.SelectCommand = cmd;

            DataTable dt = new DataTable();
            adapter.Fill(dt);

            return dt;
        }
    }
}

不能在交易中使用 DbContext.Query

Cannot Use DbContext.Query inside a transaction

c#

entity-framework

visual-studio-2015

asp.net-core