我正在制作一個(gè) UserControl 以從依賴項(xiàng)屬性生成附加文件列表作為 ItemSource。但 ItemSource (DependencyProperty) 計(jì)數(shù)為 0。我嘗試調(diào)試并意識(shí)到 ViewModel 中的 ObservableCollection 是在 UserControl 的構(gòu)造函數(shù)初始化后綁定的。我正在以 MVVM 模式進(jìn)行編碼，我創(chuàng)建了一個(gè)函數(shù)來(lái)為 ViewModel 中的 ObservableCollection 準(zhǔn)備一些示例數(shù)據(jù)，并在 MainWindow 內(nèi)將 UserControl 的 DataContext 與該 ViewModel 綁定，然后為 ObservableCollection 設(shè)置 ItemSource我的 ViewModel 代碼隱藏：//The properties ObservableCollection<FileAttachmentModel> filesAttachment; public ObservableCollection<FileAttachmentModel> FilesAttachment { get { return filesAttachment; } set { filesAttachment = value; OnPropertyChanged("FilesAttachment"); } }//The function prepare sample data private ObservableCollection<FileAttachmentModel> PrepareData() { FilesAttachment.Add(new FileAttachmentModel() { FileName = "TrackA", FilePath = "D:\trackA.png" }); FilesAttachment.Add(new FileAttachmentModel() { FileName = "TrackB", FilePath = "D:\trackB.png" }); FilesAttachment.Add(new FileAttachmentModel() { FileName = "TrackC", FilePath = "D:\trackC.png" }); }我的用戶控件 xaml：<UserControl x:Class="MailSender.Controls.FileAttachment.FileAttachment" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:local="clr-namespace:MailSender.Controls.FileAttachment" mc:Ignorable="d" d:DesignHeight="450" d:DesignWidth="800" DataContext="{Binding RelativeSource={RelativeSource Self}}" Name="fileAttachmentUC" >使用中：<control:FileAttachment DataContext="{StaticResource vmMainWindow}" ItemSource="{Binding FilesAttachment,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"/>我期望的是為附加文件制作一個(gè)容器，例如 Microsoft 的 Outlook。請(qǐng)幫忙！提前致謝！
1 回答
慕姐8265434
TA貢獻(xiàn)1813條經(jīng)驗(yàn) 獲得超2個(gè)贊
GenerateFileItem每當(dāng)使用以下方法設(shè)置依賴項(xiàng)屬性時(shí)，您都應(yīng)該調(diào)用PropertyChangedCallback：
public static readonly DependencyProperty ItemSourceProperty = DependencyProperty.Register("ItemSource",
typeof(ObservableCollection<FileAttachmentModel>), typeof(FileAttachment), new PropertyMetadata(new PropertyChangedCallback(OnChanged));
//the wrapper property
public ObservableCollection<FileAttachmentModel> ItemSource
{
get { return (ObservableCollection<FileAttachmentModel>)GetValue(ItemSourceProperty); }
set { SetValue(ItemSourceProperty, value); }
}
private static void OnChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
FileAttachment fa = (FileAttachment)d;
fa.GenerateFileItem(fa.ItemSource);
}
在初始化ItemSource之前無(wú)法設(shè)置該屬性。UserControl
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