使用ListPicker和DataBinding

问题描述

限时删除！！

好的.我放弃.我想在我的Windows Phone应用程序之一中使用ListPicker控件.我收到异常 SelectedItem必须始终设置为有效值.

Ok. I give up.I want to use ListPicker control in one of my Windows Phone apps. I am getting an Exception SelectedItem must always be set to a valid value.

这是我的XAML ListPicker:

This is my XAML piece of ListPicker:

<toolkit:ListPicker x:Name="CategoryPicker"
           FullModeItemTemplate="{StaticResource CategoryPickerFullModeItemTemplate}"
           Margin="12,0,0,0"
           ItemsSource="{Binding CategoryList}"
           SelectedItem="{Binding SelectedCategory, Mode=TwoWay}"
           ExpansionMode="ExpansionAllowed"
           FullModeHeader="Pick Categories"
           CacheMode="BitmapCache"
           Width="420"
           HorizontalAlignment="Left" />

CategoryList是我的ViewModel中的ObservableCollection<Category>.SelectedCategory是我的ViewModel中类别类型的属性.

CategoryList is an ObservableCollection<Category> in my ViewModel.SelectedCategory is a property in my ViewModel of type Category.

这就是我同时声明CategoryList和SelectedCategory的方式:

This is how I am declaring both CategoryList and SelectedCategory:

private Category _selectedCategory;// = new Category();


        private ObservableCollection<Category> _categoryList = new ObservableCollection<Category>();

        public ObservableCollection<Category> CategoryList
        {
            get
            {
                return _categoryList;
            }

            set
            {
                _categoryList = value;
                RaisePropertyChanged("CategoryList");
            }
        }


        public Category SelectedCategory
        {
            get
            {
                 return _selectedCategory;
            }
            set
            {
                if (_selectedCategory == value)
                {
                    return;
                }
                _selectedCategory = value;

                RaisePropertyChanged("SelectedCategory");
            }
        }

感谢您的帮助！！！也许我不太了解ListPicker的用法.

Appreciate your help!!! Maybe I have not understood the usage of ListPicker very well.

推荐答案

看看我对这个问题的回答:带有值转换器的Silverlight ComboBox绑定

Take a look at my answer to this question:Silverlight ComboBox binding with value converter

简短的回答是，所选项目必须是集合中包含的项目.您的获取者正在将所选项目设置为新对象.此新对象未包含在集合中

The short answer is that the selected item must be an item that is contained within the collection. Your getter is setting the selected item to a new object. This new object is not contained within the collection

这篇关于使用ListPicker和DataBinding的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！

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