C# 错误：在使用 ItemsSource 之前，Items 集合必须为空
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Error: Items collection must be empty before using ItemsSource
提问by Alexander V.
my xaml file
我的 xaml 文件
<ListBox Height="522" HorizontalAlignment="Left" Margin="20,162,0,0" Name="listBox1" VerticalAlignment="Top" Width="448" ItemsSource="{Binding}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Text}" Foreground="#FFC8AB14" FontSize="36" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
xaml.cs file
xaml.cs 文件
listBox1.Items.Clear();
for (int i = 0; i < tasks.Count(); i++) {
List<Taskonlistbox> dataSource = new List<Taskonlistbox>();
dataSource.Add(new Taskonlistbox() {Text = "Blalalalala"} );
this.listBox1.ItemsSource = dataSource; // visual stdio shows error here:
}
Taskonlistbox:
任务列表框：
public class Taskonlistbox
{
public string Text { get; set; }
}
Error: "Items collection must be empty before using ItemsSource" whats a problem?
错误：“在使用 ItemsSource 之前，项目集合必须为空”有什么问题？
采纳答案by Olivier Jacot-Descombes
You want to create the list only once and assign the data source only once! Therefore, create the list beforethe loop and assign the data source afterthe loop
您只想创建一次列表并只分配数据源一次！因此，创建列表之前的循环，并指定数据源后循环
// Clear the listbox.
// If you never add items with listBox1.Items.Add(item); you can drop this statement.
listBox1.Items.Clear();
// Create the list once.
List<Taskonlistbox> dataSource = new List<Taskonlistbox>();
// Loop through the tasks and add items to the list.
for (int i = 0; i < tasks.Count(); i++) {
dataSource.Add(new Taskonlistbox {Text = "Blalalalala"} );
}
// Assign the list to the `ItemsSouce` of the listbox once.
this.listBox1.ItemsSource = dataSource;
