我正在从 WPF View 设置到 ViewModel 对象的绑定(bind),但绑定(bind)似乎没有触发。我在 MVVM 中没有做太多工作,所以我想我想看看是否有原因导致在页面加载时绑定(bind)到图像的源属性没有触发。
这是页面的 XAML:
<Page x:Class="DallasPrintManager.PrintPage"
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:viewmodel="clr-namespace:DallasPrintManager.ViewModel"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="900"
DataContext="{Binding Main, Source={StaticResource PrintPage}}">
<Grid >
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition Width="200" />
</Grid.ColumnDefinitions>
<ScrollViewer HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">
<Image Source="{Binding ImageDisplay}" />
</ScrollViewer>
</Grid>
</Page>
这是 ViewModel:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel;
using System.Windows.Media.Imaging;
using System.Drawing;
using System.Windows.Input;
using DallasPrintManager.Commands;
using System.Net;
using System.IO;
using System.Windows;
public class PrintPageViewModel : INotifyPropertyChanged
{
private BitmapImage _imageDisplay;
public PrintPageViewModel()
{
ImageDisplay = getImage();
}
private BitmapImage getImage()
{
try
{
WebClient wc = new WebClient();
byte[] imageData = wc.DownloadData("http://localhost/TestImage.tif");
MemoryStream ms = new MemoryStream();
ms.Write(imageData, 0, imageData.Length);
System.Windows.Media.Imaging.BitmapImage wpfImg = new System.Windows.Media.Imaging.BitmapImage();
wpfImg.BeginInit();
wpfImg.StreamSource = ms;
wpfImg.EndInit();
return wpfImg;
//return (Bitmap)Bitmap.FromStream(ms);
}
catch (WebException e)
{
MessageBox.Show("Error fetching document:\n\n" + e.Message);
return null;
}
catch (Exception e)
{
if (e.Source == "System.Drawing")
MessageBox.Show("Error reading document.");
Console.Out.Write(e);
return null;
}
}
public BitmapImage ImageDisplay
{
get
{
return _imageDisplay;
}
set
{
if (value != _imageDisplay)
{
_imageDisplay = value;
OnPropertyChanged("ImageDisplay");
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this,
new PropertyChangedEventArgs(propertyName));
}
}
}
View 模型在 app.xaml 中实例化,并由打印页面绑定(bind)。
最佳答案
查看调试输出窗口。您是否看到任何绑定(bind)错误?他们几乎告诉你你需要什么。
关于c# - 为什么这个绑定(bind)在 MVVM 中不起作用?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/5808460/