使用mysql注销的C#更新代码

Question

我正在执行更新语句，其中日期时间选择器(注销)将插入到与登录相同的行中，但当我注销时它会生成另一行，这里是链接:http://imgur.com/a/rAWhi

ps。这里的问题是注销按钮插入到另一行中..但我想将其插入到同一行中。

这是我的代码:

  private void button1_Click(object sender, EventArgs e)
    {
         con.Open();
            MySqlCommand cmd = con.CreateCommand();
            cmd.CommandType = CommandType.Text;
            cmd.CommandText = "select * from empinfo where username = '" + label4.Text + "' and IDNUMBER = '" + textBox1.Text + "' ";
            cmd.ExecuteNonQuery();
            DataTable dt = new DataTable();
            MySqlDataAdapter da = new MySqlDataAdapter(cmd);
            da.Fill(dt);
            i = Convert.ToInt32(dt.Rows.Count.ToString());


            if (string.IsNullOrEmpty(textBox1.Text))
            {
                MessageBox.Show("Input your id number");


            }

            else if (i == 0)
            {

                MessageBox.Show("Username and IDNUMBER didn't match.", "Log-In Error", MessageBoxButtons.OK, MessageBoxIcon.Error);


            }
            else
            {
                updateuser();
              login frmm = new login();
                frmm.Show();
                this.Close();

            }
            con.Close();



        }
              public void updateuser()
    {
        MySqlConnection cnn = new MySqlConnection(mysqlAddress);
        MySqlCommand cmdupdate;
        cnn.Open();
        try
        {
            cmdupdate = cnn.CreateCommand();
            cmdupdate.CommandText = "update employee set logout = @logout";
            cmdupdate.CommandText = "Insert into employee (logout) values (@logout)";
            cmdupdate.Parameters.AddWithValue("@logout", dateTimePicker1.Value);

            cmdupdate.ExecuteNonQuery();
        }
        catch (Exception)
        {
            throw;
        }
        finally
        {
            if (cnn.State == ConnectionState.Open)
            {
                cnn.Close();

                MessageBox.Show("Data has been saved");
            }
        }
    }

Answer 1

正如@Ben在评论中指出的那样，您不需要使用插入而只想更新，因此请像这样更改代码:

try
        {
            cmdupdate = cnn.CreateCommand();
            cmdupdate.CommandText = "update employee set logout=@logout";
            cmdupdate.CommandText += "WHERE IDNUMBER=@IDNUMBER";
            cmdupdate.Parameters.AddWithValue("@IDNUMBER", textBox1.Text.Trim());
            cmdupdate.Parameters.AddWithValue("@logout", dateTimePicker1.Value);

            cmdupdate.ExecuteNonQuery();
        }

Where 是为了确保它只更新文本框中的 IDNUMBER。