【问题标题】:from dataGridView1.Rows.Clear() until end to my code从 dataGridView1.Rows.Clear() 直到我的代码结束
【发布时间】:2020-09-18 21:34:47
【问题描述】:

请让我解释一下我的 Visual Studio Pro 代码有一些奇怪的地方。没有断开循环的错误消息。似乎我放弃检查我的销售点项目的所有文件有什么问题。所以直到下面的代码工作正常。

 private void button1_Click(object sender, EventArgs e)
        {
            try
            {

                for (int i = 0; i < dataGridView1.Rows.Count; i++)
                {

                    MySqlCommand cmd = new MySqlCommand();
                    cmd.Connection = con;

                    cmd.CommandText = "Insert into salesproducts(saleid,productname,qty,grosstotal)values(@saleid,@productname,@qty,@grosstotal)";
                    cmd.Parameters.AddWithValue("@saleid", lbinvoice.Text);
                    cmd.Parameters.AddWithValue("@productname", dataGridView1.Rows[i].Cells[2].Value);
                    cmd.Parameters.AddWithValue("@qty", dataGridView1.Rows[i].Cells[3].Value);
                    cmd.Parameters.AddWithValue("@grosstotal", dataGridView1.Rows[i].Cells[4].Value);


                    MySqlCommand cmd1 = new MySqlCommand();
                    cmd1.Connection = con;
                    cmd1.CommandText = "insert into salesmain(id,date,time,cashername,qty,grosstotal)values(@id,@date,@time,@cashername,@qty,@grosstotal)";
                    cmd1.Parameters.AddWithValue("@id", lbinvoice.Text);
                    cmd1.Parameters.AddWithValue("@date", lbldate.Text);
                    cmd1.Parameters.AddWithValue("@time", lbltime.Text);
                    cmd1.Parameters.AddWithValue("@cashername", label6.Text);
                    cmd1.Parameters.AddWithValue("@qty", lbitems.Text);

                    cmd1.Parameters.AddWithValue("@grosstotal", lbtotal.Text);

                    con.Open();
                   int x = cmd.ExecuteNonQuery();
                   int y = cmd1.ExecuteNonQuery();

                    MessageBox.Show("Record added ..........");


                    updatedb();


                   }

               }

           catch (Exception ex)
          {
              //MessageBox.Show(ex.Message);
        }

       finally
      {
          con.Close();
      }
    }


// everything worked fine of project till now......

但是在添加这些代码之后 像现在这样然后没有任何效果。

                    updatedb();

        //Nothing worked from here...

                    dataGridView1.Rows.Clear();
                    lbtotal.Text = "0";
                    lbitems.Text = "0";
                    txtno.Focus();
                    totalPrice = 0;

                con.Close();
                invoice();
     }
           }
        catch (Exception ex)
        {
            //MessageBox.Show(ex.Message);
        }

        finally
        {
            con.Close();
        }
       }

对不起,我无法完整显示图片截图或者这里没有任何权限。请点击以下链接。

Please watch the sales window here

then please watch this one to know whats not work

我希望在不添加额外文件代码的情况下找到解决方案。谢谢

【问题讨论】:

  • 在 catch 处设置断点或者去掉 try catch 看看有没有异常!
  • 我试图在我的测试中重现该问题,但一切正常。所有的控制都可以重置。我注意到您调用了方法updatedb()invoice()。能否提供这些方法的具体代码?最好能提供一个简单的demo,能复现遇到的问题。
  • 我添加了其他信息,请在下面查看。

标签: c# .net visual-studio


【解决方案1】:

抱歉,没有完全给出代码来阐明 updateb() 和 invoice()。因此,出于这个原因,最好像我的特定文件中的所有代码一样。就这样吧。

using MySql.Data.MySqlClient;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Linq.Expressions;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace superpos3
{
    public partial class salesn : Form
    {
        public salesn()
        {
            InitializeComponent();
        }

       public static int totalPrice = 0;
        public static int payment = 0;
        public static int balance = 0;

        MySqlConnection con = new MySqlConnection("server= localhost; database =superpos;  username= root; password=; ");


        public void invoice()
        {

            con.Open();
            string query = "select max(id) from salesmain ";
            MySqlCommand cmd2 = new MySqlCommand(query, con);
            MySqlDataReader dr;
            dr = cmd2.ExecuteReader();
            if (dr.Read())
            {
                string val = dr[0].ToString();
                if (val == "")
                {
                    lbinvoice.Text = "1";

                }
                else
                {
                    int a;

                    a = int.Parse(dr[0].ToString());
                    a = a + 1;
                    lbinvoice.Text = a.ToString();



                }
                con.Close();
            }

        }





        private void richTextBox1_TextChanged(object sender, EventArgs e)
        {

        }

        private void txtno_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar == 13)
            {
                txtqty.Enabled = true;
                txtqty.Focus();
            }
        }

        private void txtqty_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar == 13)
            {

                try
                {

                    string txt = "select * from products where id='" + txtno.Text + "'";
                    MySqlCommand cmd = new MySqlCommand(txt, con);
                    con.Open();
                    MySqlDataReader r = cmd.ExecuteReader();
                    while (r.Read())
                    {
                        int price = int.Parse(txtqty.Text.ToString()) * int.Parse(r[4].ToString());
                        totalPrice = totalPrice + price;
                        //discount
                        // totalPrice = totalPrice - totalPrice* Payment.discount/100;

                        dataGridView1.Rows.Add(dataGridView1.RowCount, r[0], r[1], txtqty.Text.Trim(), r[4], price);

                    }
                    lbitems.Text = " " + (dataGridView1.RowCount - 1) + "";
                    lbtotal.Text = " " + totalPrice + " ";

                    con.Close();

                }






                catch (Exception ee)
                {
                    MessageBox.Show(ee.Message, "Error From Database");
                }

                txtno.Focus();
                txtno.Clear();

                txtqty.Enabled = false;
                txtqty.Clear();

            }

        }


        private void txtqty_TextChanged(object sender, EventArgs e)
        {

        }
        private string name;

        public string Staffname
        {
            get { return name; }
            set { name = value; }

        }



      public void updatedb()
        {

            for (int row = 0; row < dataGridView1.Rows.Count; row++)
            {


                string itmno = dataGridView1.Rows[row].Cells[1].Value.ToString();
                string itmqty = dataGridView1.Rows[row].Cells[3].Value.ToString();

                string t = "select * from products where id= '"+ itmno + "'";

                string oldqty = "", newqty = "";


                Connnew.DbSearch(t);


                while (Connnew.dr.Read())
                {

                    oldqty = Connnew.dr[5].ToString();
                    newqty = (int.Parse(oldqty) - int.Parse(itmqty)).ToString();
                }

                string t2 = "update products SET qty = '" + newqty + "' WHERE id = '" + itmno + "'";
                //t2 = t2.Replace("{0}", itmno);
                //t2 = t2.Replace("{2}", newqty);
                Connnew.DbUpdate(t2);
            }


        }


        private void salesn_Load(object sender, EventArgs e)
        {
            label6.Text = Staffname;
            lbldate.Text = DateTime.Today.ToString("dd/MM/yyyy");
            lbltime.Text = DateTime.Now.ToShortTimeString();

            invoice();

        }

        private void button1_Click(object sender, EventArgs e)
        {
            try
            {

                for (int i = 0; i < dataGridView1.Rows.Count; i++)
                {

                    MySqlCommand cmd = new MySqlCommand();
                    cmd.Connection = con;

                    cmd.CommandText = "Insert into salesproducts(saleid,productname,qty,grosstotal)values(@saleid,@productname,@qty,@grosstotal)";
                    cmd.Parameters.AddWithValue("@saleid", lbinvoice.Text);
                    cmd.Parameters.AddWithValue("@productname", dataGridView1.Rows[i].Cells[2].Value);
                    cmd.Parameters.AddWithValue("@qty", dataGridView1.Rows[i].Cells[3].Value);
                    cmd.Parameters.AddWithValue("@grosstotal", dataGridView1.Rows[i].Cells[4].Value);


                    MySqlCommand cmd1 = new MySqlCommand();
                    cmd1.Connection = con;
                    cmd1.CommandText = "insert into salesmain(id,date,time,cashername,qty,grosstotal)values(@id,@date,@time,@cashername,@qty,@grosstotal)";
                    cmd1.Parameters.AddWithValue("@id", lbinvoice.Text);
                    cmd1.Parameters.AddWithValue("@date", lbldate.Text);
                    cmd1.Parameters.AddWithValue("@time", lbltime.Text);
                    cmd1.Parameters.AddWithValue("@cashername", label6.Text);
                    cmd1.Parameters.AddWithValue("@qty", lbitems.Text);

                    cmd1.Parameters.AddWithValue("@grosstotal", lbtotal.Text);

                    con.Open();
                   int x = cmd.ExecuteNonQuery();
                   int y = cmd1.ExecuteNonQuery();

                    MessageBox.Show("Record added ..........");
                    updatedb();
                    dataGridView1.Rows.Clear();
                    lbtotal.Text = "0";
                    lbitems.Text = "0";
                    txtno.Focus();
                    totalPrice = 0;

                    con.Close();
                    invoice();

                }
               }
            catch (Exception ex)
            {
                //MessageBox.Show(ex.Message);
            }

            finally
            {
                con.Close();
            }
           }

        private void button2_Click(object sender, EventArgs e)
        {
            pay p = new pay();
            p.Show();
        }

        private void label6_Click(object sender, EventArgs e)
        {

        }
    }   
}

我看到一切都很好,但仍然没有找到问题。

和上面与 Connnew.DbSearch(t) 相关的连接,“Connnew”是这样的:

using MySql.Data.MySqlClient;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using MySql.Data.MySqlClient;
namespace superpos3
{
    class Connnew
    {

        public static MySqlConnection con = new MySqlConnection("server= localhost; database =superpos; username= root; password=; ");
        public static MySqlCommand poscmd = new MySqlCommand();
        public static MySqlDataReader dr;

        public static void DbSearch(string txt)
        {

            con.Close();
            poscmd.Connection = con;
            poscmd.CommandText = txt;
            con.Open();
            dr = poscmd.ExecuteReader();
        }

        public static void DbUpdate(string txt)
        {
            con.Close();
            poscmd.Connection = con;
            poscmd.CommandText = txt;
            con.Open();
            poscmd.ExecuteNonQuery();
        }
    }
}

请让我知道这里的代码结构问题是什么或真正出了什么问题。

【讨论】:

  • 对不起,我没有找到dataGridView1.Rows.Clear(); 不起作用的原因。但是如果要向数据库中插入多条数据,则需要将dataGridView1.Rows.Clear();移到for statement之外。
  • 你能看到我的回答出现了一些错误吗?
【解决方案2】:

我刚刚删除了 catch 块,在下面一行看到了这个错误。

// the error was pops to -->`string itmno = `dataGridView1.Rows[row].Cells[1].Value.ToString();` 

错误是:

System.NullReferenceException
      HResult=0x80004003
      Message=Object reference not set to an instance of an object.
      Source=superpos3
      StackTrace:
       at superpos3.salesn.updatedb() in D:\superpos3\superpos3\superpos3\salesn.cs:line 174
       at superpos3.salesn.button1_Click(Object sender, EventArgs e) in D:\superpos3\superpos3\superpos3\salesn.cs:line 258
       at System.Windows.Forms.Control.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ButtonBase.WndProc(Message& m)
       at System.Windows.Forms.Button.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(Form mainForm)
       at superpos3.Program.Main() in D:\superpos3\superpos3\superpos3\Program.cs:line 19

【讨论】:

  • 看来dataGridView1.Rows[row].Cells[1] 为空。也许您可以添加if statement 来检查它,或者使用Null-conditional operators
  • 您不应将updatedb 放在for statement 中。因为第一次循环执行后,datagridview中的内容已经被清空了。
  • 我到头来几乎没看懂。那么您能否告诉我如何清楚地执行 updatetb 然后向上移动到下一个 dataGridView1.Rows.Clear() 直到 invoice() 循环。
  • 如前所述,您需要在for statement 之外调用“重置控件”的代码。此外,如果你在for循环中调用updatetb,则无需在方法updatetb中使用另一个for循环。
  • 你能写一个代码的小例子吗?
猜你喜欢
  • 1970-01-01
  • 1970-01-01
  • 2017-02-22
  • 1970-01-01
  • 2018-07-17
  • 2018-04-30
  • 2018-12-06
  • 1970-01-01
  • 1970-01-01
相关资源
最近更新 更多