[英]Data Binding in MVVM WPF
我對MVVM模式知之甚少。 我的問題是數據沒有綁定到xaml控件,那里沒有錯誤。 進度欄仍為0。
主頁視圖模型
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.ComponentModel;
using CSMS_MVVM.Models;
namespace CSMS_MVVM.ViewModels
{
class HomepageViewModel : INotifyPropertyChanged
{
BackgroundWorker _worker;
public int _progress=20;
public int Progress
{
get { return _progress; }
set {
_progress = value;
OnPropertyChanged(new PropertyChangedEventArgs("Progress"));
}
}
public void startBackgroundProcess()
{
_worker = new BackgroundWorker();
_worker.DoWork += new DoWorkEventHandler(worker_DoWork);
_worker.ProgressChanged += worker_Progress_Changed;
_worker.RunWorkerAsync();
}
private void worker_Progress_Changed(object sender, ProgressChangedEventArgs e)
{
Progress = e.ProgressPercentage;
}
private void worker_DoWork(object sender, DoWorkEventArgs e)
{
Progress = 20;
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(PropertyChangedEventArgs e)
{
if (PropertyChanged != null)
PropertyChanged(this, e);
}
#endregion
}
}
Homepage.xaml.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Timers;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using CSMS_MVVM.ViewModels;
namespace CSMS_MVVM.Views
{
/// <summary>
/// Interaction logic for Homepage.xaml
/// </summary>
public partial class Homepage : Page
{
HomepageViewModel hvm;
public Homepage()
{
InitializeComponent();
}
private void Page_Loaded_1(object sender, RoutedEventArgs e)
{
hvm = new HomepageViewModel();
hvm.startBackgroundProcess();
}
}
}
Homepage.xaml
<Page x:Class="CSMS_MVVM.Views.Homepage"
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:CSMS_MVVM.ViewModels"
mc:Ignorable="d"
d:DesignHeight="700" d:DesignWidth="1000"
Title="Homepage" Loaded="Page_Loaded_1" Name="main">
<ProgressBar Name="pbStatus" Value="{Binding Path=Progress}" HorizontalAlignment="Center" Height="20" Margin="0,582,0,0" VerticalAlignment="Top" Width="300">
-----
<ProgressBar.Effect>
<DropShadowEffect Color="#FFB6B6B6" ShadowDepth="3" BlurRadius="15" Direction="310"/>
</ProgressBar.Effect>
</ProgressBar>
<TextBlock Text="{Binding Progress}" Margin="0,582,0,0" HorizontalAlignment="Center" VerticalAlignment="Top" />
<Label Content="Loading ..." HorizontalAlignment="Center" Margin="0,607,0,0" VerticalAlignment="Top"/>
------
</Page>
我在做正確的編碼嗎? 我在互聯網上搜索了一個示例,但我不理解它們。
謝謝!
如果未指定其他任何內容,則您設置的所有綁定都將綁定到DataContext
。
private void Page_Loaded_1(object sender, RoutedEventArgs e)
{
hvm = new HomepageViewModel();
hvm.startBackgroundProcess();
this.DataContext = hvm;
}
將數據上下文設置為viewmodel實例后,它應該可以工作。
您可以在后面的代碼中設置頁面的DataContext。
另一個選擇是將ViewModel創建為XAML資源,並通過數據綁定設置子元素的數據上下文:
<Page x:Class="CSMS_MVVM.Views.Homepage"
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:CSMS_MVVM.ViewModels"
mc:Ignorable="d"
d:DesignHeight="700" d:DesignWidth="1000"
Title="Homepage" Loaded="Page_Loaded_1" Name="main">
<Page.Resources>
<!-- This creates the instance of the HomepageViewModel -->
<local:HomepageViewModel x:Key="HomepageViewModel" />
</Page.Resources>
<ProgressBar DataContext="{StaticResource HomepageViewModel}"
Value="{Binding Path=Progress}">
public Homepage()
{
InitializeComponent();
hvm = new HomepageViewModel();
this.DataContext=hvm;
}
在構造函數內創建視圖模型對象。
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