Question

我正在尝试使用mysql事务保存多行数据，但是当我在指定的行执行此代码时出现错误

Using conn As New MySqlConnection(connStr)
    conn.Open()

    Using sqlTrans As MySqlTransaction = conn.BeginTransaction()

        Try
            Dim bHasRows As Boolean
            dim sSql as string

            For Each kv As KeyValuePair(Of String, String) In dicOpts
                If String.IsNullOrEmpty(kv.Key) Then Continue For
                String.format("Select * FROM Options WHERE name = '{0}';",kv.Key)
                Using cmd As New MySqlCommand(qb.GetQuery, conn)
                    bHasRows = cmd.ExecuteReader().HasRows
                End Using

                If bHasRows Then
                    ssql=String.format("UPDATE Options SET value ='{0}' WHERE name = '{1}';", kv.Value,kv.Key)
                Else
                    ssql=String.format("INSERT INTO Options(name,Value) values('{0}','{1}';",kv.Key, kv.Value)
                End If
                Using cmd As New MySqlCommand(qb.GetQuery, conn)
                    cmd.ExecuteNonQuery()    // <----- This is the error line
                End Using
            Next

        sqlTrans.Commit()
    Catch ex As Exception
        sqlTrans.Rollback()
        Throw
    Finally

    End Try
End Using

我得到的错误

已经有一个与此Connection关联的开放DataReader 必须先关闭

正如您所看到的，每次使用

都会关闭阅读器

Answer 1

这是你走错的地方：

bHasRows = cmd.ExecuteReader().HasRows

在datareader上使用Using：

Using dr = cmd.ExecuteReader()
    bHasRows = dr.HasRows
End Using

Answer 2

这正是消息所读取的内容。 bHasRows = cmd.ExecuteReader().HasRows打开DataReader并且不会关闭。正确的形式是

Using cmd As New MySqlCommand(qb.GetQuery, conn)
    Dim r = cmd.ExecuteReader()
    bHasRows = r.HasRows
    r.Close()
End Using

.net exception已经有一个与此Connection关联的打开DataReader，必须先关闭它

2 个答案: