Question

在MVVM Silverlight应用程序中，用户可以在TextBox中输入文本，ListBox内容也会相应地更改。例如：如果用户输入“TV”，ListBox将填充所有可用的电视品牌，用户可以从ListBox和ListBox条目中选择产品;接下来如果他输入“计算机”ListBox内容改变并填充ComputerNames。

一旦用户输入内容，它就会在字典中搜索值与键匹配。

查看：

<TextBox Name="SearchTBox" Text="{Binding SearchStr,UpdateSourceTrigger=PropertyChanged}" />
<ListBox Name="AnalysisLBox" ItemsSource="{Binding DataList,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"   
         SelectedItem="{Binding UserSelectedItem,Mode=TwoWay}"                                   
         Width="250" BorderBrush="Transparent" SelectedIndex="{Binding LBoxSelectedIndex,Mode=TwoWay}">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <StackPanel>
                <TextBlock Text="{Binding}" />
            </StackPanel>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

视图模型：

SortedDictionary Data()
{
    List<string> tvList = new List<string>() { "Sony", "SamSung", "LG","Sharp" };
    List<string> computerList = new List<string>() { "HP","Dell","Lenovo","Gateway" };
    List<string> cameraList = new List<string>() { "Nikon","Sony","Panasonic" };
    SortedDictionary<string, List<string>> Data = new SortedDictionary<string, List<string>>();
    Data.Add("TV", billingList);
    Data.Add("Computer", salesOutList);
    Data.Add("Camera", customerAllocationList);
}

ObservableCollection<string> dataList = new ObservableCollection<string>();
public ObservableCollection<string> DataList
{
    get { return dataList ; }
    set { dataList = value; NotifyPropertyChanged("DataList"); }
}

int lBoxSelectedIndex;
public int LBoxSelectedIndex
{
    get { return lBoxSelectedIndex; }
    set { lBoxSelectedIndex = value; NotifyPropertyChanged("LBoxSelectedIndex"); }
}

string userSelectedItem;
public string UserSelectedItem
{
    get { return userSelectedItem; }
    set
    {
        userSelectedItem = value;
    dataList.Clear(); 
        LBoxSelectedIndex =-1;
        NotifyPropertyChanged("UserSelectedItem");
    }
 }

只要一个键与用户输入的字符串（'TV'）匹配，它就会用一个绑定到ListBox的tvList填充ObservableCollection<string> dataList。用户键入Camera，它清除dataList并添加cameraList。问题出在这里。清除数据并填充新数据时，不会清除listBox的选择。先前所选位置的相同项目仍保持选中状态。我试图从ViewModel的UserSelectedItem属性中将SelectedIndex设置为-1，但它不起作用。

Answer 1

我认为你的财产可能会混乱。在ListBox中进行选择时，会触发UserSelectedItem setter并清除dataList并将LBoxSelectedIndex设置为-1。因此，当用户从ListBox中选择一个项目时，会发生什么，清除ListBox并且没有选择任何内容。

相反，似乎您应该在更改DataList时清除选择。

string userSelectedItem;
public string UserSelectedItem
{
    get { return userSelectedItem; }
    set
    {
        userSelectedItem = value;
        NotifyPropertyChanged("UserSelectedItem");
    }
}

ObservableCollection<string> dataList = new ObservableCollection<string>();
public ObservableCollection<string> DataList
{
    get { return dataList ; }
    set 
    { 
        dataList = value;
        LBoxSelectedIndex = -1;
        NotifyPropertyChanged("DataList"); 
    }
 }

当DataList更新时，您还需要清除SearchStr，并且它不等于排序字典中的任何键。

string searchStr;
public string SearchStr
{
    get { return searchStr; }
    set
    {
        searchStr = value;
        LBoxSelectedIndex = -1;
        if (string.IsNullOrEmpty(searchStr))
            DataList = null;
        else
        {
            List<string> selectedValue;
            if (Data.TryGetValue(searchStr, out selectedValue))
                DataList = new ObservableCollection<string>(selectedValue);
            else
                DataList = null;
        }
        NotifyPropertyChanged("SearchStr");
    }
}

Answer 2

您还可以在

中设置userSelectedItem=null

ObservableCollection<string> dataList = new ObservableCollection<string>();
public ObservableCollection<string> DataList
{
    get { return dataList ; }
    set 
    { 
        dataList = value;
        userSelectedItem=null
        LBoxSelectedIndex = -1;
        NotifyPropertyChanged("DataList"); 
    }
 }

ListBox MVVM中的ClearSelection

2 个答案: