How to stop DataGridView Combobox selection from disappearing

John Rutherford 21

Hi,

I have a WinForm project in .Net Framework 4.7.2

I have a class "EntryModel" that is bound to a Bindingsource "bs4".

I have a datagridview (dgvEntries) with 5 text box columns + 1 combobox column

dgvEntries.Datasource = bs5

the 5 textbox columns have their DataPropertyName from the EntryModel properties.

The Comboboxcolumn (tcode) has values assigned as follows - tcode.Items.AddRange("AAA", "BBB", "CCC");

The combobox SelectedIndex value is use the change the Rate property of the EntryModel item.

private void DgvEntries_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
        {
            combo = e.Control as ComboBox;
            if (combo != null)
            {
                combo.SelectedIndexChanged -= new EventHandler(Combo_SelectedIndexChanged);
                combo.SelectedIndexChanged += Combo_SelectedIndexChanged;
            }
        }

        private void Combo_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (combo != null)
            {
                if (combo.SelectedIndex == 0)
                {
                    EntryModel ent = (EntryModel)bs4.Current;
                    ent.Rate = 0.1m;
                }
                else
                {
                    EntryModel ent = (EntryModel)bs4.Current;
                    ent.Rate = 0m;
                }
            }
           
        }

This all works fine and the EntryModel properties are updated correctly. The problem is that the combobox selection disappears immediately after it is selected. I have traced the SelectedIndex value (for the combobox) through the above code and it is fine up until the last closing } of Combo_SelectedIndexChanged. At that point it reverts to -1.

Any help to prevent this value from disappearing is appreciated.

John

Jack J Jun 24,796 Reputation points Microsoft Vendor

2023-02-08T08:49:54.09+00:00

@John Rutherford, Welcome to Microsoft Q&A, based on my test, I could not reproduce your problem only the two pieces of code. Could you provide the related code about how do you set the Bindingsource "bs5"? Because you write the code dgvEntries.Datasource = bs5.
John Rutherford 21 Reputation points

2023-02-09T01:48:32.4533333+00:00
Hi Jack,

that line should have read dgvEntries.DataSource = bs4

My code behind the form is listed below
John Rutherford 21 Reputation points

2023-02-09T06:18:04.64+00:00
Hi Jack,

I simplified everything in the form to just the dgv, label and a button and changed the method used to add the comboboxcolumn to the datagridview.

Also changed the dgv events - removed DgvEntries_EditingControlShowing and Combo_SelectedIndexChanged from firing and replaced with

This works - of sorts. It requires a change of cell focus to fire the CellValueChanged event. I would prefer to have it fire after selecting the dropdown value.
Jack J Jun 24,796 Reputation points Microsoft Vendor

2023-02-09T07:03:29.5433333+00:00

@John Rutherford, thanks for the feedback, based on my test, I still could not reproduce your problem.

I meet the following error:

How do you set the data of bs4?

Finally, I recommend that you could simplify your code example as far as possible. And if you don't mind, you could upload your project to Onedrive or Github, then share the link here (Please remove your personal privacy).

John Rutherford 21

Hi Jack,

That line should have been dgvEntries.DataSource = bs4.

My code behind the form is attached.

using MyBank.Models;
using MyBank.Services;
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 MyBank
{
public partial class FormTransaction : Form
    {
        private AccountDAO accountDAO = new AccountDAO();
        private AccountModel account = new AccountModel();
        private TransactionDAO transactionDAO;
        private List<AccountModel> accounts;    // assetaccounts;
        private TransactionModel transaction = new TransactionModel();
        private EntryModel entry; //= new EntryModel();
        //private List<EntryModel> entries = new List<EntryModel>();
        readonly List<TaxCodeModel> taxcodes = TaxCodeModel.GetCodes();
        private BindingSource bs1;      // asset accounts
        private BindingSource bs2;      // entry accounts
        private BindingSource bs3;      // transaction
        private BindingSource bs4;      // entry
        //private BindingSource bs5;      // entries
        private BindingSource bs6;      // taxcodes
        private ComboBox combo;

        public string transtype { get; set; }

        public FormTransaction()
        {        
            InitializeComponent();
        }

        private void FormTransaction_Load(object sender, EventArgs e)
        {
            this.SuspendLayout();
            // get Accounts list and Transactions list
            accounts = accountDAO.GetAllAccounts();
            var assetaccounts = accounts.Select(x => x.FK_AccTypeId == 1);
            var entryaccounts = accounts.Select(x => x.FK_AccTypeId == 6);
            bs1 = new BindingSource();
            bs2 = new BindingSource();
            bs3 = new BindingSource();
            bs4 = new BindingSource();
            //bs5 = new BindingSource();
            bs6 = new BindingSource();
            bs1.DataSource = assetaccounts;
            bs2.DataSource = entryaccounts;
            bs3.DataSource = transaction;
            bs4.DataSource = typeof(EntryModel);    // entry;
            //bs5.DataSource = entries;
            bs6.DataSource = taxcodes;
            
            _ = bs4.AddNew() as EntryModel;
            Formatdgv();
            SetBindings();
            dgvEntries.CellClick += DgvEntries_CellClick;
            dgvEntries.DataError += DgvEntries_DataError;
            dgvEntries.EditingControlShowing += DgvEntries_EditingControlShowing;
            DeleteRow.Click += DeleteRow_Click;
            contextMenuStripDGV.Opening += ContextMenuStripDGV_Opening;

            if (transtype == "DEPOSIT") 
            {
                transaction.FK_TransactionTypeId = 1;
                this.Text = "Deposit Transaction";
            }
            else if (transtype == "WITHDRAWAL")    // WITHDRAWL
            {
                transaction.FK_TransactionTypeId = 2;
                this.Text = "Withdrawl Transaction";
            }
            this.ResumeLayout();
        }

private void DgvEntries_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
        {
            combo = e.Control as ComboBox;
            if (combo != null)
            {
                combo.SelectedIndexChanged -= new EventHandler(Combo_SelectedIndexChanged);
                combo.SelectedIndexChanged += Combo_SelectedIndexChanged;
            }
        }

        private void Combo_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (combo != null)
            {
                if (combo.SelectedIndex == 0)
                {
                    EntryModel ent = (EntryModel)bs4.Current;
                    ent.TaxRate = 0.1m;
                }
                else
                {
                    EntryModel ent = (EntryModel)bs4.Current;
                    ent.TaxRate = 0m;
                }
            }
           
        }

        private void ContextMenuStripDGV_Opening(object sender, CancelEventArgs e)
        {
            var mousepos = Control.MousePosition;
            if (sender is ContextMenuStrip cms)
            {
                var rel_mousePos = cms.PointToClient(mousepos);
                if (cms.ClientRectangle.Contains(rel_mousePos))
                {
                    //the mouse pos is on the menu ... 
                    //looks like the mouse was used to open it
                    var dgv_rel_mousePos = dgvEntries.PointToClient(mousepos);
                    var hti = dgvEntries.HitTest(dgv_rel_mousePos.X, dgv_rel_mousePos.Y);
                    if (hti.RowIndex == -1)
                    {
                        // no row ...
                        e.Cancel = true;
                    }
                }
                else
                {
                    //looks like the menu was opened without the mouse ...
                    //we could cancel the menu, or perhaps use the currently selected cell as reference...
                    e.Cancel = true;
                }
            }
        }

        private void DeleteRow_Click(object sender, EventArgs e)
        {
            Int32 rowToDelete = dgvEntries.Rows.GetFirstRow(DataGridViewElementStates.Selected);
            dgvEntries.Rows.RemoveAt(rowToDelete);
            bs4.RemoveAt(rowToDelete);
            //bs5.RemoveAt(rowToDelete);
            //bs5.ResetBindings(false);
            dgvEntries.ClearSelection();
        }

        private void DgvEntries_CellClick(object sender, DataGridViewCellEventArgs e)
        {
            if (e.RowIndex >= 0)
            {
                if (dgvEntries.SelectedRows.Count != 0)
                {
                    _ = this.dgvEntries.SelectedRows[0];
                    bs4.Position = e.RowIndex;
                }
            }
        }

        private void DgvEntries_DataError(object sender, DataGridViewDataErrorEventArgs anError)
        {
            MessageBox.Show("Error happened " + anError.Context.ToString());

            if (anError.Context == DataGridViewDataErrorContexts.Commit)
            {
                MessageBox.Show("Commit error - value must be positive numeric");
            }
            if (anError.Context == DataGridViewDataErrorContexts.CurrentCellChange)
            {
                MessageBox.Show("Cell change");
            }
            if (anError.Context == DataGridViewDataErrorContexts.Parsing)
            {
                MessageBox.Show("parsing error - value must be positive numeric");
            }
            if (anError.Context == DataGridViewDataErrorContexts.LeaveControl)
            {
                MessageBox.Show("leave control error");
            }

            if ((anError.Exception) is ConstraintException)
            {
                DataGridView view = (DataGridView)sender;
                view.Rows[anError.RowIndex].ErrorText = "an error";
                view.Rows[anError.RowIndex].Cells[anError.ColumnIndex].ErrorText = "an error";

                anError.ThrowException = false;
            }
        }

        private void DgvEntries_CellValidating(object sender, DataGridViewCellValidatingEventArgs e)
        {
            try
            {
                if (e.RowIndex < 0) return;     // abort if header row

                switch (e.ColumnIndex)
                {
                    case 0:
                        break;
                    case 3:
                        if (!decimal.TryParse(e.FormattedValue.ToString(), out decimal amt) || amt < 0)
                        {
                            MessageBox.Show("Value must be numeric and positive");
                        }
                        break;
                    case 5:
                        if (!decimal.TryParse(e.FormattedValue.ToString(), out decimal amt5) || amt5 < 0)
                        {
                            MessageBox.Show("Value must be numeric and positive");
                        }
                        break;
                    default:
                        break;
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show("Exception in Validating: " + ex.Message);
            }
        }

        //private void DgvEntries_CurrentCellDirtyStateChanged(object sender, EventArgs e)
        //{
        //        if (dgvEntries.IsCurrentCellDirty)
        //    {
        //        this.dgvEntries.CommitEdit(DataGridViewDataErrorContexts.Commit);
        //    }
        //}

        private void SetBindings()
        {
            // set transaction bindings elements
            txtTransactionNumber.DataBindings.Add("text", bs3, "ChequeNumber");
            dtpDate.DataBindings.Add("Value", bs3, "TrDate", true, DataSourceUpdateMode.OnValidation, DateTime.Now, "ddd d MMM yyyy");
            txtMemo.DataBindings.Add("text", bs3, "TrMemo");
            CboAssetAccount.DisplayMember = "AccName";
            CboAssetAccount.ValueMember = "AccNumber";
            CboAssetAccount.DataSource = bs1;

            // individual transaction details
            CboEntryAccount.DisplayMember = "AccName";
            CboEntryAccount.ValueMember = "AccNumber";
            CboEntryAccount.DataSource = bs2;

            //CboEntryTaxCode.DisplayMember = "TaxCode";
            //CboEntryTaxCode.ValueMember = "TaxRate";   // PK_TaxCodeId
            //CboEntryTaxCode.DataSource = bs6;
            //Binding trate = new Binding("SelectedValue", bs4, "TaxRate", false, DataSourceUpdateMode.OnPropertyChanged);
            //CboEntryTaxCode.DataBindings.Add(trate);

            //TxtEntryMemo.DataBindings.Add("text", bs4, "EntryMemo");
            //Binding tea = new Binding("text", bs4, "EntryAmount", true)
            //{
            //    FormatString = "c"
            //};
            //TxtEntryAmt.DataBindings.Add(tea);
            //Binding tetax = new Binding("text", bs4, "TaxAmount", true)
            //{
            //    FormatString = "c"
            //};
            //TxtEntryTaxAmt.DataBindings.Add(tetax);
            //Binding tetfa = new Binding("text", bs4, "TaxFreeAmount", true)
            //{
            //    FormatString = "c"
            //};
            //TxtEntryTaxFreeAmt.DataBindings.Add(tetfa);
        }

        private void CboAssetAccount_SelectedIndexChanged(object sender, EventArgs e)
        {
            // show the account name in lblAssetAccountName
            ComboBox senderComboBox = (ComboBox)sender;

            if (senderComboBox.SelectedIndex > 0)
            {
                AccountModel account = accountDAO.GetAccountbyId(senderComboBox.ValueMember);
                var names = accounts.Where(x => x.AccNumber == senderComboBox.ValueMember).Select(x => x.AccName);
                var bal = accounts.Where(x => x.AccNumber == senderComboBox.ValueMember).Select(x => x.Balance);
                if (names.Count() == 1)
                {
                    lblAssetName.Text = names.ElementAt(0);
                    lblAssetBalance.Text = string.Format("{0:c}",bal.ElementAt(0));
                }
            }
            // show the Asset Account Balance in lblAssetBalance
        }

        private void BtnAddEntry_Click(object sender, EventArgs e)
        {
            decimal sum = 0;

            //bs4.Add(entry);
            bs4.ResetBindings(false);

            _ = bs4.AddNew() as EntryModel;
            bs4.ResetBindings(false);
            foreach (EntryModel ent in bs4)
            {
                sum += ent.EntryAmount;
            }
            txtTotalAmt.Text = string.Format("{0:C}", sum);
        }

        private void Formatdgv()
        {
            try
            {
                dgvEntries.AutoGenerateColumns = false;
                dgvEntries.BackgroundColor = Color.Beige;
                dgvEntries.BackColor = System.Drawing.Color.Beige;
                dgvEntries.AllowUserToAddRows = false;
                dgvEntries.AllowUserToDeleteRows = false;
                dgvEntries.AllowUserToOrderColumns = false;
                dgvEntries.ShowCellToolTips = true;
                dgvEntries.RowHeadersVisible = true;
                dgvEntries.MultiSelect = false;
                dgvEntries.SelectionMode = DataGridViewSelectionMode.CellSelect;
                dgvEntries.DataSource = bs4; 
                dgvEntries.RowHeadersDefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleCenter;

                DataGridViewTextBoxColumn notes = new DataGridViewTextBoxColumn();
                DataGridViewTextBoxColumn acct = new DataGridViewTextBoxColumn();
                DataGridViewComboBoxColumn tcode = new DataGridViewComboBoxColumn();
                DataGridViewTextBoxColumn taxamount = new DataGridViewTextBoxColumn();
                DataGridViewTextBoxColumn taxfreeamount = new DataGridViewTextBoxColumn();
                DataGridViewTextBoxColumn amount = new DataGridViewTextBoxColumn();

                notes.Name = "memo";
                acct.Name = "acct";
                tcode.Name = "taxcode";
                taxamount.Name = "taxamount";
                taxfreeamount.Name = "taxfreeamount";
                amount.Name = "amount";

                notes.HeaderText = "Memo";
                acct.HeaderText = "Account";
                tcode.HeaderText = "Tax Code";
                taxamount.HeaderText = "Tax Amount";
                taxfreeamount.HeaderText = "Tax Free Amount";
                amount.HeaderText = "Amount";

                notes.DataPropertyName = "EntryMemo";
                acct.DataPropertyName = "ExpAccount";
                tcode.DataPropertyName = "TaxCode";
                taxamount.DataPropertyName = "TaxAmount";
                taxfreeamount.DataPropertyName = "TaxFreeAmount";
                amount.DataPropertyName = "EntryAmount";

                notes.FillWeight = 5;
                acct.FillWeight = 1;
                tcode.FillWeight = 1;
                taxamount.FillWeight = 1;
                taxfreeamount.FillWeight = 1;
                amount.FillWeight = 1;

                taxamount.ReadOnly = true;
                taxfreeamount.ReadOnly = true;

                tcode.Items.AddRange("GST", "GST Free");

                dgvEntries.Columns.AddRange(notes, acct, tcode, taxamount, taxfreeamount, amount);
                
                //dgvEntries.Columns[2].ValueType = Type.GetType("System.Decimal");
                dgvEntries.Columns[3].ValueType = Type.GetType("System.Decimal");
                dgvEntries.Columns[4].ValueType = Type.GetType("System.Decimal");
                dgvEntries.Columns[5].ValueType = Type.GetType("System.Decimal");

                dgvEntries.Columns[2].DefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleCenter;
                dgvEntries.Columns[3].DefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleCenter;
                dgvEntries.Columns[4].DefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleRight;
                dgvEntries.Columns[5].DefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleRight;
                
                //dgvEntries.Columns[2].DefaultCellStyle.Format = "P2";
                dgvEntries.Columns[3].DefaultCellStyle.Format = "C2";
                dgvEntries.Columns[4].DefaultCellStyle.Format = "C2";
                dgvEntries.Columns[5].DefaultCellStyle.Format = "C2";

                dgvEntries.AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.Fill;
            }
            catch (Exception e)
            {
                MessageBox.Show(string.Format("{0} Exception caught.", e),"dgv");
            }
        }

        private void BtnCancel_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void BtnRecord_Click(object sender, EventArgs e)
        {
            // validate entries
            // add entries to list
            transactionDAO = new TransactionDAO();
            EntryDAO entryDAO = new EntryDAO();
            int transnum = transactionDAO.Insert(transaction);
            
            foreach (DataGridViewRow row in dgvEntries.Rows)
            {
                entry = new EntryModel
                {
                    FK_TransactionId = transnum,
                    FK_AccountId = (string)row.Cells[1].Value,
                    EntryMemo = (string)row.Cells[0].Value,
                    EntryAmount = (decimal)row.Cells[5].Value,
                    FK_TaxCodeId = (int)row.Cells[2].Value,
                    TaxRate = (decimal)row.Cells[3].Value,
                };
                int entryKey = entryDAO.Insert(entry);
            }
            // TO DO
            // add the Tax amount to the resp. Tax account


            // update asset account balance

        }
    }
}

John Rutherford 21 Reputation points

2023-02-10T05:56:48.5633333+00:00

Hi Jack,

Solution simplified and uploaded to OneDrive.

https://1drv.ms/u/s!AkLgkYjj9ahSjWxPDaywPqVM_Lfb?e=J8slTd

The issue is with the Transaction Formdgv now where as you add more "line items" the combobox text value in previous lines disappears.

I appreciate your help.

John

1 answer

John Rutherford 21 Reputation points

2023-02-10T05:56:32.0333333+00:00
Hi Jack,

I've finally cracked this problem.

Had to reference my EntryModel entry

then use this when I create the first line item for the bindingsource bs1

entry = bs1.AddNew() as EntryModel;

and then reference the "entry" in the CellValueChanged event

entry = (EntryModel)bs1.Current;
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