Visual Studio / WPF > DataGrid > 最後に選択した行を削除する

```txt:動作環境
Windows 7 Pro (32bit)
Microsoft Visual Studio 2017 Community
```

以下の実装をした。

- DataGridにおいて選択
- Deleteボタンを押す
    - 選択した行を消す

lastIndexを取得している理由は、削除ボタンを押した時点で「.SelectedItem」が見えなくなるため。

参考: https://stackoverflow.com/questions/9743420/remove-an-item-from-an-observablecollection-in-a-collectionchanged-event-handler

もっと良い実装方法はありそうだ。

### code

```MainWindow.xaml.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
//
using System.IO;
using System.Globalization;
using System.Data;
using System.Collections.ObjectModel;

namespace _170611_t1030_readCsvFile
{
    /// <summary>
    /// MainWindow.xaml の相互作用ロジック
    /// </summary>
    public partial class MainWindow : Window
    { 
        static readonly int kIndex_notSelected = -1;
        private int lastIndex = kIndex_notSelected; // DataGridの最後の選択
        private ObservableCollection<Person> myList;

        public MainWindow()
        {
            InitializeComponent();
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            myList = new ObservableCollection<Person>();
            myList.Add(new Person { Name = "7of9", Race = "Borg", Codename = "seven" });
            myList.Add(new Person { Name = "Janeway", Race = "Human", Codename = "Captain" });
            myList.Add(new Person { Name = "Odo", Race = "Unknown", Codename = "Odo" });
            this.DataContext = myList;
        }

        private void B_delete_Click(object sender, RoutedEventArgs e)
        {
            if (lastIndex == kIndex_notSelected)
            {
                return;
            }
            Person prsn = dg1.Items[lastIndex] as Person;
            myList.Remove(prsn);

            MessageBox.Show("deleted " + prsn.Name);
            lastIndex = kIndex_notSelected;
        }

        private void dg1_MouseLeave(object sender, MouseEventArgs e)
        {
            DataGrid dgc = sender as DataGrid;
            if (dgc == null)
            {
                return;
            }
            lastIndex = dgc.SelectedIndex;
        }
    }

    // Name, Race, Codename
    public class Person
    {
        public string Name { get; set; }
        public string Race { get; set; }
        public string Codename { get; set; }
    }

}
```

```MainWindow.xaml
<Window x:Class="_170611_t1030_readCsvFile.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:_170611_t1030_readCsvFile"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525" Loaded="Window_Loaded">
    <Window.Resources>
        <Style x:Key="keyCellStyle" TargetType="DataGridCell">
            <Style.Triggers>
                <Trigger Property="TabIndex" Value="0">
                    <Setter Property="Background" Value="LightGreen"/>
                </Trigger>
                <Trigger Property="TabIndex" Value="1">
                    <Setter Property="Background" Value="LightGreen"/>
                </Trigger>
            </Style.Triggers>
        </Style>
    </Window.Resources>
    <Grid>
        <StackPanel>
            <Button x:Name="B_delete" Content="delete"
                    Click="B_delete_Click" Width="100"/>
            <DataGrid Height="300" x:Name="dg1"
                      AutoGenerateColumns="True"
                      IsReadOnly="true"
                      CellStyle="{StaticResource keyCellStyle}"
                      ItemsSource="{Binding}" MouseLeave="dg1_MouseLeave"/>
        </StackPanel>
    </Grid>
</Window>
```

Odoを選択。
![2017-06-11_17h16_58.png](https://qiita-image-store.s3.amazonaws.com/0/32870/501fee22-813a-8070-b12a-3938731b4928.png)

Deleteボタンを押下。
Odoが削除される。
![2017-06-11_17h17_07.png](https://qiita-image-store.s3.amazonaws.com/0/32870/af3c3296-1cac-bdd4-0d2a-a23f6b7c9186.png)


### より良いUI

左列にcheckboxを用意して、選択した行を消す。

LINQで処理することになるのだろうか。