在sqltransaction中是否类似

问题描述

SqlConnection cn;
SqlTransaction st;
st=cn.BeginTransaction;

V/s

SqlConnection cn;
SqlTransaction st =新的SqlTransaction();


相似吗?

我尝试过的事情:

我曾在Google上搜索过，但没有理解并感到困惑.

V/s

SqlConnection cn;
SqlTransaction st=new SqlTransaction();


Is it similar?

What I have tried:

I had searched on google but not understand and confused.

private void btbsend_Click(object sender, EventArgs e)
        {
                MySqlCommand genvoucher,df;
                MySqlTransaction genvouchrt=new MySqlTransaction();
                MySqlTransaction dft = new MySqlTransaction();
                try
                {
                    cn.Open();

                    string fvno;
                    dateTimePicker1.Value = DateTime.Now;
                    dateTimePicker2.Value = DateTime.Now;
                    var tdat = dateTimePicker2.Value;
                    var ttime = dateTimePicker1.Value;
                    fvno = textBox1.Text;
                    genvoucher = new MySqlCommand("insert into cutting(vno,bno,nsize,machine,vdate,operator,stime,shift,status) values(@vno,@bno,@size,@machine,@date,@opt,@start,@shift,@status)", cn, genvouchrt);
                    genvoucher.Parameters.AddWithValue("@vno", fvno);
                    genvoucher.Parameters.AddWithValue("@size", textBox3.Text);
                    genvoucher.Parameters.AddWithValue("@bno", comboBox3.SelectedItem.ToString());
                    genvoucher.Parameters.AddWithValue("@machine", comboBox1.SelectedItem.ToString());
                    genvoucher.Parameters.AddWithValue("@date", tdat);
                    genvoucher.Parameters.AddWithValue("@opt", comboBox4.SelectedItem.ToString());
                    genvoucher.Parameters.AddWithValue("@shift", shift);
                    genvoucher.Parameters.AddWithValue("@start", ttime);
                    genvoucher.Parameters.AddWithValue("@status", "Open");
                    genvoucher.ExecuteNonQuery();
                    genvouchrt.Commit();

                    df = new MySqlCommand("insert into vouchers values(@vno,@dept,@shift,@task,@stats,@remarkn,@remarkv)", cn, dft);
                    df.Parameters.AddWithValue("@vno", textBox1.Text);
                    df.Parameters.AddWithValue("@dept", dept);
                    df.Parameters.AddWithValue("@shift", shift);
                    df.Parameters.AddWithValue("@task", "Cutting");
                    df.Parameters.AddWithValue("@stats", "Open");
                    df.Parameters.AddWithValue("@remarkn", "");
                    df.Parameters.AddWithValue("@remarkv", "");
                    df.ExecuteNonQuery();
                    dft.Commit();

                    MessageBox.Show("Voucher Opened Successfully!");
                    cn.Close();

                    this.Close();
                }
            catch (Exception eli)
            {
                MessageBox.Show("Can''t Generate Voucher" + Environment.NewLine + eli);
                try
                {
                    genvouchrt.Rollback();
                    dft.Rollback();
                }
                catch(Exception ex)
                {
                    MessageBox.Show("Rollback Exception"+ex.Message);
                }
            }
        }

推荐答案

SqlConnection cn;
SqlTransaction st;
st=cn.BeginTransaction;

V/s

V/s

SqlConnection cn;
SqlTransaction st=new SqlTransaction();

但是，由于后一个问题尚未编译，因此该问题不太合理.换句话说，您不能直接实例化SqlTransaction类.这是因为构造函数定义为internal.

如果您尝试编译后面的代码，则会收到错误消息

However, the question does not quite make sense since the latter one does not compile. In other words, you cannot instantiate a SqlTransaction class directly. This is because the constructor is defined as internal.

If you try to compile the latter code you''ll get an error

Severity Code   Description
-------- ------ ----------------------------------------------------------------------
Error    CS1729 ''SqlTransaction'' does not contain a constructor that takes 0 arguments	

阻止直接实例化SqlTransaction类的原因可能是，在BeginTransaction调用期间，执行了一些检查并进行了分配，例如:
-如果未指定，则默认隔离级别设置为读取已提交
-连接已验证
-如果需要恢复连接并断开连接
-等等...

Probably the reason for preventing direct instantiation of SqlTransaction class is that during BeginTransaction call, several checks are carried out and assignments made, for example:
- default isolation level is set to read committed if not specified
- connection is validated
- the connection is restored if needed and broken
- and so on...

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