Question

下面是我用于MySqlTransaction的代码，它运行得很好.... 但问题是因为我使用的是mysql命令的单个实例，我必须在其中使用唯一的PARAMETER。这毁了我的查询。还有其他方法吗....

我尝试在每次查询后处置cmd但没有用.. :(

          con.Open()
            Dim sqlTran As MySqlTransaction = con.BeginTransaction()
            Dim cmd As MySqlCommand = con.CreateCommand()
            cmd.Transaction = sqlTran
            Dim str As String = Nothing
            Try
                cmd.CommandText = "SELECT myid FROM memaster where    Adate=@adate and ANo=@ano and ASource=@asrc"
                cmd.Parameters.AddWithValue("@adate", txt_bpass_adate.Text)
                cmd.Parameters.AddWithValue("@ano", txt_bpass_af.Text)
                cmd.Parameters.AddWithValue("@asrc", txt_bpass_asource.Text)
                str = cmd.ExecuteScalar()
                'cmd.Dispose()'
                If str Is Nothing Then

                    cmd.CommandText = "Insert into memaster (ADate,ANo,ASource) values (@aDate,@aNo,@aSRC)"
                    cmd.Parameters.AddWithValue("@aDate", txt_bpass_adate.Text)
                    cmd.Parameters.AddWithValue("@aNo", txt_bpass_af.Text)
                    cmd.Parameters.AddWithValue("@aSRC", txt_bpass_asource.Text)

     cmd.ExecuteNonQuery()
    End If
     sqlTran.Commit()

            Catch ex As Exception
                Try
                    sqlTran.Rollback()
                Catch ex1 As Exception

                End Try
            End Try

我实际上想要在单个事务中触发超过4个查询，这样如果出现任何问题我可以回滚它...

如果有人有任何其他方法，请与我分享这个概念......

     For index As Integer = 1 To 5
                    cmd.CommandText = "Insert into detail (ID,BNos,SNo) values (@FID1,@BNo,@SeqN1)"
                    cmd.Parameters.AddWithValue("@FID1", str)
                    cmd.Parameters.AddWithValue("@BNo", str1)
                    cmd.Parameters.AddWithValue("@SeqN1", txt_bpass_sqn1.Text)
                    cmd.ExecuteNonQuery()


                Next

Answer 1

要在同一事务中执行多个命令，请确保将事务对象分别分配给每个命令：

Dim selectCmd As MySqlCommand = con.CreateCommand()
Dim insertCmd As MySqlCommand = con.CreateCommand()

selectCmd.CommandText = "SELECT ..."
insertCmd.CommandText = "INSERT ..."

Dim sqlTran As MySqlTransaction = con.BeginTransaction()
Try
  selectCmd.Transaction = sqlTran
  insertCmd.Transaction = sqlTran

  ...selectCmd.ExecuteScalar()...
  ...insertCmd.ExecuteNonQuery()...

  sqlTran.Commit()
Catch
  sqlTran.Rollback()
End Try

正如其他人所提到的那样，Dispose()对象（IDisposable）一旦完成它们，通常是个好主意。处理完对象后，将无法再使用它们。

Answer 2

您可以使用Using关键字来自动配置对象。我不懂VB但我知道C＃。请将代码转换为VB。

using(MySqlConnection con= new MySqlConnection("connectionString"))
{
    con.Open();
    using(MysqlTransaction trans=con.BeginTransaction())
    {
        try
        {
            //command to executive query
            using(MysqlCommand cmd= new MySqlCommand("query", con, trans))
            {
                cmd.Parameters.AddWithValue("@parameter1", parametervalue1);
                cmd.Parameters.AddWithValue("@parameter2", parametervalue2);
                cmd.ExecutenonQuery();
                cmd.Parameters.Clear();
            }
            //command to execute query
            using(MysqlCommand cmd= new MySqlCommand("query", con, trans))
            {
                cmd.Parameters.AddWithValue("@parameter1", parametervalue1);
                cmd.Parameters.AddWithValue("@parameter2", parametervalue2);
                cmd.ExecutenonQuery();
                cmd.Parameters.Clear();
            }
            //command to execute query
            using(MysqlCommand cmd= new MySqlCommand("query", con, trans))
            {
                cmd.Parameters.AddWithValue("@parameter1", parametervalue1);
                cmd.Parameters.AddWithValue("@parameter2", parametervalue2);
                cmd.ExecutenonQuery();
                cmd.Parameters.Clear();
            }
            trans.Commit();
        }
        catch(Exception ex)
        {
            trans.Rollback();
        }
    }
}

mysql事务（提交和回滚）

2 个答案: