使用 ItemsSource 时操作无效.使用 ItemsControl.ItemsSource 访问和修改元素 [英] Operation is not valid while ItemsSource is in use. Access and modify elements with ItemsControl.ItemsSource instead

问题描述

我最近刚接触 Binding 和 WPF 我学会了如何使用 Binding 技术创建具有多列的 listBox

I am new in Binding and WPF recently I've learned how to create a listBox with multiple columns using Binding tech

 <ListView ItemsSource="{Binding Items}" Margin="306,70,22,17" MouseDoubleClick="listBoxSS_MouseDoubleClick" Name="listBoxSS" >           
    <ListView.View>
            <GridView>
                <GridView.Columns>
                    <GridViewColumn Header="first_name " Width="100" DisplayMemberBinding="{Binding Path=First_name}" />
                    <GridViewColumn Header="last_name" Width="100" DisplayMemberBinding="{Binding Path=Last_name}" />
                    <GridViewColumn Header="phone_number" Width="100" DisplayMemberBinding="{Binding Path=Phones[0]}" />
                    <GridViewColumn Header="notes" Width="100" DisplayMemberBinding="{Binding Path=Notes}" />
                </GridView.Columns>
            </GridView>
        </ListView.View>
    </ListView>

这是代码:

List<Student> arr = search.students();
        listBoxSS.ItemsSource = arr;

但问题是当我尝试使用添加或删除项目或清除

but the problem was when I tried to use add or remove item or clear

 listBoxSS.Items.Clear();

请我需要一个示例来使用项目源或我可以添加或删除项目或清除列表的方式.

Please I need an example for using the items source or the way that I can ADD or Remove Item or Clear the list.

<ListView ItemsSource="{Binding Items}" Margin="306,70,22,17" MouseDoubleClick="listBoxSS_MouseDoubleClick" Name="listBoxSS" >
    <ListView.View>
        <GridView>
            <GridView.Columns>
                <GridViewColumn Header="first_name " Width="100" DisplayMemberBinding="{Binding Path=First_name}" />
                <GridViewColumn Header="last_name" Width="100" DisplayMemberBinding="{Binding Path=Last_name}" />
                <GridViewColumn Header="phone_number" Width="100" DisplayMemberBinding="{Binding Path=Phones[0]}" />
                <GridViewColumn Header="notes" Width="100" DisplayMemberBinding="{Binding Path=Notes}" />
            </GridView.Columns>
        </GridView>
    </ListView.View>
</ListView>

这是代码:

 ObservableCollection<Employee> Gemployees;
var employees = new ObservableCollection<Employee>(search.employees());

search.employees() 获取我数据库中所有员工的列表

search.employees() get the list of all employees in my DB

 listBoxPE.ItemsSource = employees;
        Gemployees = employees;

现在我可以对 Gemployees 执行所有方法

now I can perform all the methods on Gemployees

 Gemployees.Remove((Student)listBoxSS.SelectedItem);
 Gemployees.Add((Student)listBoxSS.SelectedItem);

每当我从 Gemployees 添加或删除项目时，ListView 都会执行刷新！！很酷，但在绑定方面仍然有点困难.现在我正在为每个 ListView 做一个接口类，这样我就可以把我的东西放进去.它不会在添加项目方面表现出任何灵活性.

The ListView perform a refresh whenever I add or remove an Item from Gemployees!! Cool but still a little hard work on binding. Now I am doing an interface class to every ListView so I can put my stuff into it. It wont perform any flexibility in Adding Items.

推荐答案

您正在将 ItemsSource 绑定到名为 Items 的 DataContext 属性code>，所以要更新集合，你需要去DataContext中的Items属性并清除它.

You're binding the ItemsSource to a property in the DataContext called Items, so to update the collection, you need to go to the Items property in the DataContext and clear it.

此外，Items 属性需要是 ObservableCollection 类型，而不是 List集合更改.

In addition, the Items property needs to be of type ObservableCollection, not List if you want it to update the UI whenever the underlying collection changes.

您在后面的代码中设置 ItemsSource 的代码是不需要的，应该删除.您只需要在一处设置 ItemsSource，而不是同时设置.

Your bit of code that sets the ItemsSource in the code behind is not needed and should be removed. You only need to set the ItemsSource in one place, not both.

这里有一个简单的例子来说明它是如何工作的:

Here's a simple example of how it can work:

// Using Students instead of Items for the PropertyName to clarify
public ObservableCollection<Student> Students { get; set; }

public MyConstructor()
{
    ...

    Students = search.students();
    listBoxSS.DataContext = this;
}

现在当你有:

<ListView ItemsSource="{Binding Students}" ... />

您正在将 ItemsSource 绑定到 ObservableCollection，当您想清除列表时，您可以调用:

you're binding the ItemsSource to the ObservableCollection<Student>, and when you want to clear the list you can call:

Students.Clear()

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