C# 如何从Xamrin.Form中的ListView和ViewModelObserverAgeCollection中删除项？

我想从Xamrin.Form中的ListView和ViewModelObserverAgeCollection中删除项

雇员结果

<ListView x:Name="EmployeeResultsListView"
          ItemsSource="{Binding EmployeeResults}"
          RowHeight="200"
          IsPullToRefreshEnabled="true"
          RefreshCommand="{Binding RefreshDataCommand}"
          IsRefreshing="{Binding IsRefreshingData, Mode=OneWay}"
          ItemAppearing="Employee_ItemAppearing"
    <ListView.ItemTemplate>
        <DataTemplate>
            <local:EmployeeResultViewCell />
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

---

更改：删除单击事件并添加绑定。

对于MVVM，您不使用事件，而是使用viewmodels中的命令，您可以将这些命令绑定到视图的命令。要实现您想要的功能，最有效的MVVM方法是在单元格中添加一个

ICommand

bindable属性

public partial class EmployeeResultViewCell : CustomViewCell
{
    /// <summary>
    ///   The <see cref="DeleteCommand" /> bindable property.
    /// </summary>
    public static readonly BindableProperty DeleteCommandProperty = BindableProperty.Create(nameof(SealCheckListPage.DeleteCommand), typeof(ICommand), typeof(SealCheckListPage), default(ICommand));

    /// <summary>
    ///   Gets or sets the DeleteCommand that is called when we'd like to delete an employee.
    /// </summary>
    public ICommand DeleteCommand
    {
        get => (ICommand)this.GetValue(SealCheckListPage.DeleteCommandProperty);

        set => this.SetValue(SealCheckListPage.DeleteCommandProperty, value);
    }

    private void MenuItemDelete_Clicked(object sender, System.EventArgs e)
    {
        DeleteCommand?.Execute(BindingContext);
    }
}

请注意，包含

列表视图的页面必须具有
x:Name=“page”
，才能正确绑定命令。诚然，以这种方式绑定命令并不是最理想的，但据我所知，这是我们所能做的最好的，MVVM方面的

最后一件事是将
ICommand
属性添加到viewmodel中

<ListView>
    <ListView.ItemTemplate>
        <DataTemplate>
            <local:EmployeeResultViewCell DeleteCommand="{Binding BindingContext.DeleteCommand, Source={x:Reference Page}}" />
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

public class EmployeeResultsViewModel : ViewModelBase
{
    private async Task LoadEmployee()
    {
        EmployeeResults = GetDataUsingAPI(); //15 records per call

        DeleteCommand = new Command<ExtendedEmployee>(OnDelete);
    }

    public ICommand DeleteCommand { get; }

    private void OnDelete(ExtendedEmployee employee)
    {
        // delete the employee from the collection
    }

    /* ... */
}

public类EmployeeResultsViewModel:ViewModelBase
{
私有异步任务LoadEmployee（）
{
EmployeeResults=GetDataUsingAPI（）；//每次调用15条记录
DeleteCommand=新命令（OnDelete）；
}
公共ICommand DeleteCommand{get；}
私有void OnDelete（扩展雇员）
{
//从集合中删除该员工
}
/* ... */
}

现在，当您的单元格接收到事件时，它将执行命令，该命令绑定到viewmodel中的命令。执行此命令时，它将执行传递的委托
OnDelete
，在该委托中，您可以访问要从中删除
ExtendedEmployee
的集合。
您好，非常感谢。我已经在菜单项中编辑了我的问题和设置命令。但我仍然无法调用ListPage的ViewModel命令。你能纠正我吗。我认为这行菜单项中有问题
Command=“{Binding Path=BindingContext.OnDeleteEmployeeCommand，Source={x:Reference EmployeeResultsPage}}”
@NanjiMange您检查过调试输出了吗？如果绑定失败，应该有一条调试消息告诉您失败的原因。此外，通过在此处设置断点来检查
MenuItemDelete\u是否单击了
。您是否为
DeleteCommand
创建了属性和
BindableProperty
（或者根据您的喜好简单地创建
Command
），它工作正常。非常感谢你。你救了我一天。
public partial class EmployeeResultViewCell : CustomViewCell
{
    /// <summary>
    ///   The <see cref="DeleteCommand" /> bindable property.
    /// </summary>
    public static readonly BindableProperty DeleteCommandProperty = BindableProperty.Create(nameof(SealCheckListPage.DeleteCommand), typeof(ICommand), typeof(SealCheckListPage), default(ICommand));

    /// <summary>
    ///   Gets or sets the DeleteCommand that is called when we'd like to delete an employee.
    /// </summary>
    public ICommand DeleteCommand
    {
        get => (ICommand)this.GetValue(SealCheckListPage.DeleteCommandProperty);

        set => this.SetValue(SealCheckListPage.DeleteCommandProperty, value);
    }

    private void MenuItemDelete_Clicked(object sender, System.EventArgs e)
    {
        DeleteCommand?.Execute(BindingContext);
    }
}

<ListView>
    <ListView.ItemTemplate>
        <DataTemplate>
            <local:EmployeeResultViewCell DeleteCommand="{Binding BindingContext.DeleteCommand, Source={x:Reference Page}}" />
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

public class EmployeeResultsViewModel : ViewModelBase
{
    private async Task LoadEmployee()
    {
        EmployeeResults = GetDataUsingAPI(); //15 records per call

        DeleteCommand = new Command<ExtendedEmployee>(OnDelete);
    }

    public ICommand DeleteCommand { get; }

    private void OnDelete(ExtendedEmployee employee)
    {
        // delete the employee from the collection
    }

    /* ... */
}