C# 用于绑定的xaml术语的差异
我是使用Silverlight的xaml(用于MVVM方法)的初学者。我读了几份文件,对这一切都有点困惑。如果有人能解释一下以下两者之间的区别,我将不胜感激 假设我的XAML是:C# 用于绑定的xaml术语的差异,c#,.net,silverlight,xaml,mvvm,C#,.net,Silverlight,Xaml,Mvvm,我是使用Silverlight的xaml(用于MVVM方法)的初学者。我读了几份文件,对这一切都有点困惑。如果有人能解释一下以下两者之间的区别,我将不胜感激 假设我的XAML是: xmlns:viewmodel="clr-namespace:smallMVVM" ...... ...... <UserControl.Resources> <viewmodel:ViewModel x:Key="ViewModel"/> &l
xmlns:viewmodel="clr-namespace:smallMVVM"
......
......
<UserControl.Resources>
<viewmodel:ViewModel x:Key="ViewModel"/>
<viewmodel:DatetimeToDateConverter x:Key="MyConverter"/>
</UserControl.Resources>
xmlns:viewmodel=“clr命名空间:smallMVVM”
......
......
现在,这两者之间的区别是什么:
“this.DataContext=newviewmodel();”
。在MainPage.xaml中执行以下操作。这两者有什么区别吗ItemsSource=“{StaticResource customers}”
。ItemSource
与DataContext
有何不同。然而,我可以在示例(1)
中看到,我在DataContext的绑定中有相同的内容(请参见:Source={StaticResource ViewModel}
,在(2)
中,它被客户
替换)。两者有什么不同ItemsSource=“{Binding Students}”
里面没有StaticResource
。它与StaticResource有什么不同Binding=“{Binding Name}”
SelectedItem
和SelectedValue
有何不同Partial Public Class MainPage
Inherits UserControl
Private _viewModel As TestViewModel
Public Sub New()
InitializeComponent()
_viewModel = TryCast(Resources("TheViewModel"), TestViewModel)
Me.DataContext = _viewModel
End Sub
End Class
2) 您不希望将ItemsSource设置为静态页面资源,而是希望将其设置为ViewModel中的属性。下面是一个示例视图和视图模型,请注意VM上的继承和推进,它们允许VM告诉您的视图属性已更改,并重新加载属性
视图:
上面的关键部分是Me.OnPropertyChanged(“SampleCollection”)
,它告诉视图更新绑定到的属性
关于体系结构的说明,如果要构建具有多个视图和视图模型的应用程序,请创建一个ViewModelBase并使其继承DependencyObject并实现INotifyPropertyChanged,那么所有真实视图模型都可以从ViewModelBase继承
我还创建了一个名为TestModel的类,该类在VM中使用,但保留为空。该模型是您将代码放在与DB对话的地方,或者我所做的是调用与我的DB对话的WCF服务
5) 最后,SelectedItem是所选ItemSource中的实际对象,而SelectedValue是SelectedValuePath的值。
在上面的示例中,我创建了一个简单的字符串集合,但假设您有一个具有多个属性的自定义对象集合,则可以将SelectedValuePath指定为这些属性之一。SelectedItem将返回整个对象
<UserControl x:Class="SilverlightTestApp.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="400"
xmlns:navigation="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Navigation"
xmlns:ModelViewModel="clr-namespace:SilverlightTestApp" >
<UserControl.Resources>
<ModelViewModel:TestViewModel x:Key="TheViewModel" />
</UserControl.Resources>
<Grid x:Name="LayoutRoot" Background="White" DataContext="{StaticResource TheViewModel}">
<ItemsControl ItemsSource="{Binding SampleCollection}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding}"></TextBlock>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
Imports System.ComponentModel
Imports System.Collections.ObjectModel
Public Class TestViewModel
Inherits DependencyObject
Implements System.ComponentModel.INotifyPropertyChanged
Implements INotifyDataErrorInfo
Private _model As TestModel
Sub New()
Me.New(New TestModel)
End Sub
Public Sub New(ByVal model As TestModel)
_model = model
_sampleCollection = New ObservableCollection(Of String)
_sampleCollection.Add("one")
_sampleCollection.Add("two")
_sampleCollection.Add("three")
_sampleCollection.Add("four")
End Sub
Private _sampleCollection As ObservableCollection(Of String)
Public Property SampleCollection As ObservableCollection(Of String)
Get
Return _sampleCollection
End Get
Set(value As ObservableCollection(Of String))
If value IsNot Nothing Then
_sampleCollection = value
End If
Me.OnPropertyChanged("SampleCollection")
End Set
End Property
Public Event PropertyChanged(sender As Object, e As PropertyChangedEventArgs) Implements INotifyPropertyChanged.PropertyChanged
Protected errors As New Dictionary(Of String, List(Of String))
Protected Sub OnPropertyChanged(ByVal propertyName As String)
RaiseEvent PropertyChanged(Me, New System.ComponentModel.PropertyChangedEventArgs(propertyName))
End Sub
' #Region " Validation Plumbing"
' Adds the specified error to the errors collection if it is not
' already present, inserting it in the first position if isWarning is
' false. Raises the ErrorsChanged event if the collection changes.
Public Sub AddError(ByVal propertyName As String, ByVal [error] As String,
ByVal isWarning As Boolean)
If Not errors.ContainsKey(propertyName) Then _
errors(propertyName) = New List(Of String)()
If Not errors(propertyName).Contains([error]) Then
If isWarning Then
errors(propertyName).Add([error])
Else
errors(propertyName).Insert(0, [error])
End If
RaiseErrorsChanged(propertyName)
End If
End Sub
' Removes the specified error from the errors collection if it is
' present. Raises the ErrorsChanged event if the collection changes.
Public Sub RemoveError(ByVal propertyName As String, ByVal [error] As String)
If errors.ContainsKey(propertyName) AndAlso
errors(propertyName).Contains([error]) Then
errors(propertyName).Remove([error])
If errors(propertyName).Count = 0 Then errors.Remove(propertyName)
RaiseErrorsChanged(propertyName)
End If
End Sub
Public Sub RemoveError(ByVal propertyName As String)
If errors.ContainsKey(propertyName) Then
errors.Remove(propertyName)
RaiseErrorsChanged(propertyName)
End If
End Sub
Public Sub RaiseErrorsChanged(ByVal propertyName As String)
OnPropertyChanged("HasErrors")
RaiseEvent ErrorsChanged(Me,
New DataErrorsChangedEventArgs(propertyName))
End Sub
Public Event ErrorsChanged As EventHandler(Of DataErrorsChangedEventArgs) _
Implements INotifyDataErrorInfo.ErrorsChanged
Public Function GetErrors(ByVal propertyName As String) _
As System.Collections.IEnumerable _
Implements INotifyDataErrorInfo.GetErrors
If (String.IsNullOrEmpty(propertyName) OrElse
Not errors.ContainsKey(propertyName)) Then Return Nothing
Return errors(propertyName)
End Function
Public ReadOnly Property HasErrors As Boolean _
Implements INotifyDataErrorInfo.HasErrors
Get
Return errors.Count > 0
End Get
End Property
End Class