其他文本框文本更改时，如何自动更改文本框文本？

Question

I have these textboxes named bags,rate,quantity,packing size and amount what i want to do is that when user enters bags and rate and packing size the quantity textbox should automatically shows the corresponding quantity and amount but in my case when i click on calculate button then it calculates and show the quantity and amount i have tried using textchanged event but it does not do the job?

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

namespace Login
{
    public partial class Sale : Form
    {
        SaleCalci sale;
        SaleBillheader SaleHeaderModel = new SaleBillheader();
        tbl_SaleBillDetails SaleDetailModel = new tbl_SaleBillDetails();



        public Sale()
        {
            InitializeComponent();
        }

        private void Cancelbtn_Click(object sender, EventArgs e)
        {
            clear();
        }

        private void clear()
        {
            txtBillNo.Text = txtDesc.Text = "";
            txtBags.Text = txtQty.Text = txtRate.Text = txtAmt.Text = "0.00";
            if(txtQty.Text !=null &&  txtAmt.Text !=null )
            {
                txtQty.Text = "0.00";
                txtAmt.Text = "0.00";
            }
            Savebtn.Text = "Save";
            SaleHeaderModel.SaleBillHeaderId = 0;
            SaleDetailModel.SaleBill_Id = 0;
        }

        private void Exitbtn_Click(object sender, EventArgs e)
        {
           var result =  MessageBox.Show("Are you sure you want to close this form ?", "Confirm", MessageBoxButtons.YesNo);
           if (result == DialogResult.Yes)
           { this.Close(); }


        }

        private void Sale_Load(object sender, EventArgs e)
        {
            ItemCombo();
            PartyCombo();
            PackingSizeCombo();

           // clear();
        }

        private void ItemCombo()
        {
            UserDataEntities db = new UserDataEntities();
            Itembox.DataSource = db.tbl_ItemId.ToList();
            Itembox.ValueMember = "ItemId";
            Itembox.DisplayMember = "ItemName";

        }
        private void PartyCombo()
        {
            UserDataEntities db = new UserDataEntities();
            PartyBox.DataSource = db.tbl_Parties.ToList();
            PartyBox.ValueMember = "Id";
            PartyBox.DisplayMember = "PartyName";

        }
        private void PackingSizeCombo()
        {
            UserDataEntities db = new UserDataEntities();
            PackingBox.DataSource = db.PackingSizes.ToList();
            PackingBox.ValueMember =  "PackingSizeId";
            PackingBox.DisplayMember = "PackingSize1";
        }

        private void Savebtn_Click(object sender, EventArgs e)
        {
            CalculateAmount();
            DisplayAmt();
        }
        private void CalculateAmount()
        {
            int bags = 0;
            decimal rate = 0;
            int pksize = 0;

            bags = Convert.ToInt32(txtBags.Text);
            rate = Convert.ToDecimal(txtRate.Text);
            pksize = Convert.ToInt32(PackingBox.Text);

            sale = new SaleCalci(bags,rate, pksize);

            //sale.Bags = Convert.ToInt32(txtBags.Text);
            //sale.Rate = Convert.ToDecimal(txtRate.Text);


            //SaleDetailModel.Bags = int.Parse(txtBags.Text.Trim());
            //SaleDetailModel.Qty = Convert.ToDecimal(txtQty.Text.Trim());
            //SaleDetailModel.Rate = Convert.ToDecimal(txtRate.Text.Trim());
           // SaleDetailModel.Amount = amount;






        }

        private void txtAmt_TextChanged(object sender, EventArgs e)
        {
           // txtAmt.Text = sale.CalucalteAmt.ToString();
        }

        private void Sale_Click(object sender, EventArgs e)
        {
            if ((txtBags.Text == "0.00") && (txtQty.Text == "0.00")&&(txtRate.Text == "0.00")&& (txtAmt.Text =="0.00"))
            {
                txtAmt.Clear();
                txtBags.Clear();
                txtQty.Clear();
                txtRate.Clear();
            }
        }

        private void txtQty_TextChanged(object sender, EventArgs e)
        {

            DisplayAmt();

        }

        private void txtBags_TextChanged(object sender, EventArgs e)
        {

           // sale.Bags = Convert.ToInt32(txtBags.Text);
           // DisplayAmt();
        }

        private void PackingBox_SelectedIndexChanged(object sender, EventArgs e)
        {

        }

        private void txtRate_TextChanged(object sender, EventArgs e)
        {

           // DisplayAmt();
        }

        private void DisplayAmt()
        {
            decimal _amt = sale.CalucalteAmt;
            txtQty.Text = sale.CalculateQty().ToString();
            txtAmt.Text = _amt.ToString();

        }


    }


}

Answer 1

Normally "TextChanged" event fires autamatically if text value changes.

So here the problem is i think about your other "partial class" in which there has to exist eventhandler work. Something like:

txtBags.TextChanged += new EventHandler(txtBags_TextChanged);

Please check your other partial class if this staement exist.

This eventhandler sometimes disappears from project if you move your gui elements or for some other causes...

You can readd this statement manually.

By the way if you have not experience with the other partial class then you can try to remove these textboxes and re-add them then your problem will autamatically solves.

Answer 2

You need to call DisplayAmt in the TextChanged event of txtBags , txtRate and Size. In the code above, call to DisplayAmt is commented out. Instead, you are calling DisplayAmt in the TextChanged event of txtQty.

You should be, instead doing.

private void txtAmt_TextChanged(object sender, EventArgs e)
{
   DisplayAmt();
}

private void txtRate_TextChanged(object sender, EventArgs e)
{
   DisplayAmt();
}

Similarly, you need to add Changed event for Text Control for Size. The txtQty is updated by the DisplayAmt() method. So you don't necessarily need it, unless for reasons that are not specified in OP.