删除绑定到 ObservableCollection 的 DataGrid 中的选定行

Question

我正在用 WPF 编写一个应用程序，尝试使用 MVVM 设计模式（这对我来说是新的）。我有一个 DataGrid 绑定到一个 ObservableCollection.

我想要达到的目标：

使用 'Delete' 按钮删除当前选定的 DataGrid 行。我尝试了过多的论坛帖子和视频来寻找解决方案。这个解决方案可能已经让我眼前一亮好几次了，但此时我比刚开始时更加困惑。

如有任何帮助，我们将不胜感激。

ViewModel（更新了工作代码，感谢 EldHasp）：

using System;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Windows;
using GalaSoft.MvvmLight.CommandWpf;
using Ridel.Hub.Model;

namespace Ridel.Hub.ViewModel {

    public class LicenseHoldersViewModel : INotifyPropertyChanged {

        public ObservableCollection<LicenseHolders> licenseHolders { get; }
            = new ObservableCollection<LicenseHolders>();
        

        public LicenseHoldersViewModel() {

            FillDataGridLicenseHolders();
        }

        private void FillDataGridLicenseHolders() {

            try {

                using (SqlConnection sqlCon = new(ConnectionString.connectionString))
                using (SqlCommand sqlCmd = new("select * from tblLicenseHolder", sqlCon))
                using (SqlDataAdapter sqlDaAd = new(sqlCmd))
                using (DataSet ds = new()) {

                    sqlCon.Open();
                    sqlDaAd.Fill(ds, "tblLicenseHolder");

                    //if (licenseHolders == null)
                        //licenseHolders = new ObservableCollection<LicenseHolders>();

                    foreach (DataRow dr in ds.Tables[0].Rows) {

                        licenseHolders.Add(new LicenseHolders {

                            ID = Convert.ToInt32(dr[0].ToString()),
                            Foretaksnavn = dr[1].ToString(),
                            Foretaksnummer = dr[2].ToString(),
                            Adresse = dr[3].ToString(),
                            Postnummer = (int)dr[4],
                            Poststed = dr[5].ToString(),
                            BIC = dr[6].ToString(),
                            IBAN = dr[7].ToString(),
                            //Profilbilde ???
                            Kontaktperson = dr[8].ToString(),
                            Epost = dr[9].ToString(),
                            Tlf = dr[10].ToString()
                        });
                    }
                }

            } catch (Exception ex) {

                MessageBox.Show(ex.Message, "Message", MessageBoxButton.OK, MessageBoxImage.Information);
            }
        }

        private RelayCommand<LicenseHolders> _removeLicenseHoldersCommand;

        public RelayCommand<LicenseHolders> RemoveLicenseHoldersCommand => _removeLicenseHoldersCommand
            ?? (_removeLicenseHoldersCommand = new RelayCommand<LicenseHolders>(RemoveLicenseHolderExecute, RemoveLicenseHolderCanExecute));

        private bool RemoveLicenseHolderCanExecute(LicenseHolders myLicenseHolder) {

            // Checking for the removeable licenseholder in the collection
            return licenseHolders.Contains(myLicenseHolder);
        }

        private void RemoveLicenseHolderExecute(LicenseHolders myLicenseHolder) {

                licenseHolders.Remove(myLicenseHolder);
        }

        public event PropertyChangedEventHandler PropertyChanged;

        private void OnPropertyChanged(string propertyName) {

            if (PropertyChanged != null) {

                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }
}

型号：

public class LicenseHolders {

    public string example { get; set; }
    // more of the same...
}

XAML:

<Button Style="{DynamicResource ButtonWithRoundCornersGreen}" 
    FontSize="22" x:Name="btnDelete" Content="Delete" 
    Width="187" Height="47" Background="#48bb88" Foreground="White" 
    Canvas.Left="547" Canvas.Top="668" IsEnabled="False" Click="btnDelete_Click"/>

<DataGrid             
    x:Name="dgLicenseHolder"
    CanUserAddRows="False"
    ItemsSource="{Binding licenseHolders}"
    Height="557" 
    Width="505" 
    ColumnWidth="*"
    Canvas.Top="158" 
    FontSize="20"
    IsReadOnly="True"
    SelectionMode="Single"
    AutoGenerateColumns="False"
    CanUserDeleteRows="False"
    SelectionChanged="dgLicenseHolder_SelectionChanged" Canvas.Left="31" >

    <DataGrid.Columns>
        <DataGridTextColumn Header="Example" Binding="{Binding Path='Example'}" IsReadOnly="True" Visibility="Collapsed"/>
        // more of the same..
    </DataGrid.Columns>            
</DataGrid>

代码隐藏：

public partial class Personell : Window {

    LicenseHoldersViewModel licenseHoldersViewModel;

    public Personell() {

        InitializeComponent();

        licenseHoldersViewModel = new LicenseHoldersViewModel();
        base.DataContext = licenseHoldersViewModel;
    }
}

Answer 1

您可以使用棱镜。在你的项目中安装包 Prism.Core 然后 Install-Package Microsoft.Xaml.Behaviors.Wpf -Version 1.1.31 包，在你的 xaml 中声明命名空间为 - xmlns:i="http://schemas.microsoft.com/xaml/behaviors"

<Button Content="Button">
        <i:Interaction.Triggers>
            <i:EventTrigger EventName="Click">
                <i:InvokeCommandAction Command="{Binding MyCommand }" 
                            CommandParameter="{Binding PassRow/IDHere}" />
            </i:EventTrigger>
        </i:Interaction.Triggers>
    </Button>

在您的 ViewModel 中 -

public class ViewModel
{
    public ICommand MyCommand { get; set; }

    public ViewModel()
    {
        MyCommand = new DelegateCommand<object>(OnRowDeleted);
    }

    public void OnRowDeleted(object o)
    {
        // remove the value from your observablecollection here using LINQ
    }
}

Answer 2

由于您使用的是 MVVM，因此不应使用按钮事件 Click 处理程序来操作 ViewModel 数据。
为此，您必须在 ViewModel 中创建命令 -属性并将其绑定到按钮。
命令参数绑定到 SelectedItem（如果选择 Single 模式并且只删除一个选定的行），或者绑定到 SelectedItems（如果选择 Extended 模式并且删除多行）。

我不知道您使用的是 INotifyPropertyChanged 和 ICommand 的哪些实现。
因此，我正在编写一个基于我自己实现的 .

的示例

    public class LicensesViewModel : BaseInpc
    {
        // A collection-property of the ObservableCollection type is best done «ReadOnly».
        public ObservableCollection<LicenseHolders> LicensesHolders { get; }
            = new ObservableCollection<LicenseHolders>();
        public void FillDataGrid()
        {

            //---------------
            //---------------
            //---------------

                //if (licenseHolders == null)
                //    licenseHolders = new ObservableCollection<LicenseHolders>();

                foreach (DataRow dr in ds.Tables[0].Rows)
                {

                    LicensesHolders.Add(new LicenseHolders
                    {

                        example = dr[0].ToString(),
                        // more of the same...

                    });
                }
            }
        }


        private RelayCommand _removeLicenseCommand;
        public RelayCommand RemoveLicenseCommand => _removeLicenseCommand
            ?? (_removeLicenseCommand = new RelayCommand<LicenseHolders>(RemoveLicenseExecute, RemoveLicenseCanExecute));

        private bool RemoveLicenseCanExecute(LicenseHolders license)
        {
            // Checking for the Removable License in the Collection
            return LicensesHolders.Contains(license);
        }

        private void RemoveLicenseExecute(LicenseHolders license)
        {
            // If necessary, the code for removing the license from the database is placed at the beginning of the method.
            // For example, calling some method for this, returning true if the deletion is successful.
            var result = RemoveFromBD(license);

            //It is then removed from the collection.
            if (result)
                LicensesHolders.Remove(license);
        }

        private bool RemoveFromBD(LicenseHolders license)
        {
            throw new NotImplementedException();
        }
    }

<Button Style="{DynamicResource ButtonWithRoundCornersGreen}" 
    FontSize="22" x:Name="btnDelete" Content="Delete" 
    Width="187" Height="47" Background="#48bb88" Foreground="White" 
    Canvas.Left="547" Canvas.Top="668" IsEnabled="False"
    Command="{Binding RemoveLicenseCommand}"
    CommandParameter="{Binding SelectedItem, ElementName=dgLicenseHolder}"/>

多选模式的实现选项：

        private RelayCommand _removeLicensesCommand;
        public RelayCommand RemoveLicensesCommand => _removeLicensesCommand
            ?? (_removeLicensesCommand = new RelayCommand<IList>(RemoveLicensesExecute, RemoveLicensesCanExecute));

        private bool RemoveLicensesCanExecute(IList licenses)
        {
            // Checking for the Removable License in the Collection
            return licenses.OfType<LicenseHolders>().Any(license => LicensesHolders.Contains(license));
        }

        private void RemoveLicensesExecute(IList licenses)
        {
            foreach (var license in licenses.OfType<LicenseHolders>().ToArray())
            {
                var result = RemoveFromBD(license);

                if (result)
                    LicensesHolders.Remove(license);
            }
        }

<Button Style="{DynamicResource ButtonWithRoundCornersGreen}" 
    FontSize="22" x:Name="btnDelete" Content="Delete" 
    Width="187" Height="47" Background="#48bb88" Foreground="White" 
    Canvas.Left="547" Canvas.Top="668" IsEnabled="False"
    Command="{Binding RemoveLicensesCommand}"
    CommandParameter="{Binding SelectedItems, ElementName=dgLicenseHolder}"/>

Update! (when trying to implement the solution of 'EldHasp' Error message

错误是由于使用 MVVMLight。
您最初没有表明您正在使用这个包。
其中，RelayCommand 不是 RelayCommand<T>.
的基础因此，属性和变量的类型必须与使用的构造函数的类型匹配。

这就是您需要 MVVMLight 的方式：

    private RelayCommand<LicenseHolders> _removeLicenseHoldersCommand;

    public RelayCommand<LicenseHolders> RemoveLicenseHolderCommand => _removeLicenseHoldersCommand
        ?? (_removeLicenseHoldersCommand = new RelayCommand<LicenseHolders>(RemoveLicenseHolderExecute, RemoveLicenseHolderCanExecute);

有关分配 DataContext 的其他建议。

XAMLDesigner 在设计时不处理在代码隐藏中分配它。因此，在开发过程中，您看不到 UI 元素在数据传输到它们时的外观。
这非常不方便。
要解决这个问题，需要设置Development Time DataContext。
但是在简单的情况下，你只需要在 XAML.

中设置 DataContext

清除背后的代码：

public partial class Personell : Window 
{
    public Personell() => InitializeComponent();
}

添加到 XAML:

<Window.DataContext>
  <local:LicenseHoldersViewModel/>
</Window.DataContext>

删除绑定到 ObservableCollection 的 DataGrid 中的选定行

Delete selected row in DataGrid bound to an ObservableCollection

c#

wpf

xaml

datagrid

observablecollection

我想要达到的目标：