Observable Collection 如果存在则编辑项目，否则添加新项目

Question

我的窗口中有一些文本框，点击 btn_add 后它们的内容将被添加到 Observable Collection 中，然后将成为 dg_VoucherDetail 的来源。 问题是： 当我第一次使用它时一切都很好，但第二次它只是替换旧的 Observable 集合，除了向旧集合添加新项目， 对于编辑部分，集合中没有要搜索和编辑的项目。 这是代码：

    private void btn_add_Click(object sender, RoutedEventArgs e)
    {
        _VoucherDetail = new ObservableCollection<VoucherDetail>();
        VoucherDetail Voucher = new VoucherDetail();

        if (dg_VoucherDetail.HasItems == true)
        {
            for (int i = 0; i < _VoucherDetail.Count; i++)
            {
                if (_VoucherDetail[i].LedgerID == SelectedLedgerID)
                {
                    if (_VoucherDetail[i].DefinitiveID == SelectedDefinitiveID)
                    {
                        if (_VoucherDetail[i].Credit == Convert.ToDecimal(txt_Amount.Text))
                            return;
                        else if (_VoucherDetail[i].Debit == Convert.ToDecimal(txt_Amount.Text))
                            return;
                        else
                        {
                            Voucher.LedgerID = SelectedLedgerID;
                            Voucher.DefinitiveID = SelectedDefinitiveID;
                            if (radio_debit.IsChecked == true)
                            {
                                Voucher.Debit = Convert.ToDecimal(txt_Amount.Text);
                                Voucher.Credit = 0;
                            }
                            else if (radio_credit.IsChecked == true)
                            {
                                Voucher.Debit = 0;
                                Voucher.Credit = Convert.ToDecimal(txt_Amount.Text);
                            }
                            _VoucherDetail[i] = Voucher;
                        }
                    }
                    else if (_VoucherDetail[i].DefinitiveID != SelectedDefinitiveID)
                    {
                        Voucher.LedgerID = SelectedLedgerID;
                        Voucher.DefinitiveID = SelectedDefinitiveID;
                        if (radio_debit.IsChecked == true)
                        {
                            Voucher.Debit = Convert.ToDecimal(txt_Amount.Text);
                            Voucher.Credit = 0;
                        }
                        else if (radio_credit.IsChecked == true)
                        {
                            Voucher.Debit = 0;
                            Voucher.Credit = Convert.ToDecimal(txt_Amount.Text);
                        }
                        _VoucherDetail.Add(Voucher);
                    }
                }
                else if (_VoucherDetail[i].LedgerID != SelectedLedgerID)
                {
                    Voucher.LedgerID = SelectedLedgerID;
                    Voucher.DefinitiveID = SelectedDefinitiveID;
                    if (radio_debit.IsChecked == true)
                    {
                        Voucher.Debit = Convert.ToDecimal(txt_Amount.Text);
                        Voucher.Credit = 0;
                    }
                    else if (radio_credit.IsChecked == true)
                    {
                        Voucher.Debit = 0;
                        Voucher.Credit = Convert.ToDecimal(txt_Amount.Text);
                    }
                    _VoucherDetail.Add(Voucher);
                }
            }
        }
        if (dg_VoucherDetail.HasItems == false)
        {
            Voucher.LedgerID = SelectedLedgerID;
            Voucher.DefinitiveID = SelectedDefinitiveID;
            if (radio_debit.IsChecked == true)
            {
                Voucher.Debit = Convert.ToDecimal(txt_Amount.Text);
                Voucher.Credit = 0;
            }
            else if (radio_credit.IsChecked == true)
            {
                Voucher.Debit = 0;
                Voucher.Credit = Convert.ToDecimal(txt_Amount.Text);
            }
            _VoucherDetail.Add(Voucher);
  //          dg_VoucherDetail.Items.Add(VoucherDetail);
        }
        dg_VoucherDetail.ItemsSource = _VoucherDetail;
    }


    internal class VoucherDetail
{
    public decimal LedgerID { get; set; }
    public decimal DefinitiveID { get; set; }
    public decimal Debit { get; set; }
    public decimal Credit { get; set; }
}

Answer 1

这是一个简单的 sn-p，如果条目存在于集合中，它会“更新”条目。这个 sn-p 有一些东西是硬编码的，但让它动态化应该是微不足道的。

using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Collections.ObjectModel;

namespace UpdateObservableCollection_47291451
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {

        DataGrid dg = new DataGrid();
        Button btn = new Button();
        ObservableCollection<VoucherDetail> datasource = new ObservableCollection<VoucherDetail>();
        public MainWindow()
        {
            InitializeComponent();
            dg.Height = 200;
            dg.Width = 500;
            MainGrid.Children.Add(dg);//add DataGrid to page
            btn.Content = "Click me";
            btn.Click += Btn_Click;
            btn.Height = 25;
            btn.Width = 50;
            MainGrid.Children.Add(btn);//add button to page

            dg.ItemsSource = datasource;//bind grid to data

            //create initial data records
            for (int i = 0; i < 5; i++)
            {
                datasource.Add(new UpdateObservableCollection_47291451.VoucherDetail { Credit = i, Debit = i, DefinitiveID = i, LedgerID = i });
            }
        }

        private void Btn_Click(object sender, RoutedEventArgs e)
        {
            //if a record with DefinitiveID of 1 exist, then update the entry
            if (datasource.FirstOrDefault(p => p.DefinitiveID == 1) != null)
            {
                datasource.First(p => p.DefinitiveID == 1).Credit = 1234;
                dg.Items.Refresh();
            }
            else
            {
                datasource.Add(new UpdateObservableCollection_47291451.VoucherDetail { DefinitiveID = 99, Credit = 99, Debit = 99, LedgerID = 99 });
            }
        }
    }


    internal class VoucherDetail
    {
        public decimal LedgerID { get; set; }
        public decimal DefinitiveID { get; set; }
        public decimal Debit { get; set; }
        public decimal Credit { get; set; }
    }


}