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
。
使用“删除”按钮删除当前选定的 DataGrid 行。 我已经尝试了大量的论坛帖子和视频来找到解决方案。 该解决方案可能已经多次直视我的脸,但此时我比刚开始时更困惑。
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));
}
}
}
}
模型:
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;
}
}
答案 0 :(得分:1)
由于您使用的是 MVVM,因此您不应使用按钮事件 Click 处理程序来操作 ViewModel 数据。
为此,您必须在 ViewModel 中创建一个命令属性并将其绑定到按钮。
命令参数绑定到 SelectedItem(如果选择了 Single 模式并且只删除了一个选定的行),或者绑定到 SelectedItems(如果选择了扩展模式并删除了多行)。
我不知道您使用的是 INotifyPropertyChanged 和 ICommand 的哪些实现。
因此,我正在根据我自己的 the BaseInpc and RelayCommand classes 实现编写一个示例。
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}"/>
多选模式的一个实现选项:
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}"/>
<块引用>
更新! (在尝试实施“EldHasp”的解决方案时 错误信息
错误是由于使用了 MVVMLight。
您最初并未表明您正在使用此软件包。
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相匹配。
这就是 MVVMLight 需要它的方式:
private RelayCommand<LicenseHolders> _removeLicenseHoldersCommand;
public RelayCommand<LicenseHolders> RemoveLicenseHolderCommand => _removeLicenseHoldersCommand
?? (_removeLicenseHoldersCommand = new RelayCommand<LicenseHolders>(RemoveLicenseHolderExecute, RemoveLicenseHolderCanExecute);
关于分配 DataContext 的其他建议。
XAML 设计器在设计时不处理在代码隐藏中分配它。
因此,您在开发过程中看不到数据传输到 UI 元素时的外观。
这非常不方便。
要解决这个问题,需要设置Development Time DataContext。
但在简单的情况下,您只需要在 XAML 中设置 DataContext 即可。
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>
答案 1 :(得分:0)
您可以使用棱镜。 Intall package Prism.Core 然后在你的项目中安装 Install-Package Microsoft.Xaml.Behaviors.Wpf -Version 1.1.31
个包,在你的 xaml 中将命名空间声明为 - 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>
在您的视图模型中 -
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
}
}