我创建了一个用户控件,在app周围的多个地方使用它,控件有两个属性,女巫值被绑定到viewmodel。问题是,当应用程序加载它时,在设置用户控件的一个属性时抛出异常,任何想法?
用户Control.xaml
<UserControl x:Class="Client.Controls.CredentialsUserControl"
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"
FontFamily="{StaticResource PhoneFontFamilyNormal}"
FontSize="{StaticResource PhoneFontSizeNormal}"
Foreground="{StaticResource PhoneForegroundBrush}"
d:DesignHeight="480" d:DesignWidth="480">
<Grid Name="LayoutRoot">
<TextBlock Text="{Binding Title}" Margin="12,20,12,390" TextWrapping="Wrap" FontSize="30"/>
<TextBlock Text="Username" Margin="39,88,260,362" FontSize="25"/>
<TextBlock Text="{Binding Credentials.User}" Margin="361,88,0,362" FontSize="25" />
<TextBlock Text="Password" Margin="39,148,260,302" FontSize="25"/>
<TextBlock Text="{Binding Credentials.Password}" Margin="361,148,0,302" FontSize="25" />
</UserControl>
UserControl.xaml.cs
public partial class CredentialUserControl: UserControl , INotifyPropertyChanged
{
public const string CredentialsPropertyName = "Credentials";
private ICredentials _credentials= null;
public ICredentials Credentials
{
get
{
_credentials_report;
}
set
{
if (_credentials== value)
{
return;
}
_credentials= value;
NotifyPropertyChanged(CredentialsPropertyName );
}
}
public string Title { get; set; }
public MobfoxReportUserControl()
{
InitializeComponent();
Loaded += PageLoaded;
}
void PageLoaded(object sender, RoutedEventArgs e)
{
this.DataContext = this;
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(string prop)
{
if(PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(prop));
}
}
用法:
<Controls:CredentialsUserControl Title="Your Credentials" Credentials="{Binding CurrentUser}"/>
ViewModel属性片段与UserControl.xaml.cs中显示的相同
抛出异常
System.Windows.Markup.XamlParseException occurred
Message=Set property 'CredentialsUserControl.Credentials' threw an exception. [Line: 29 Position: 85]
InnerException: System.ArgumentException
Message=ArgumentException
StackTrace:
at System.Reflection.RuntimeMethodInfo.InternalInvoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, StackCrawlMark& stackMark)
at System.Reflection.RuntimePropertyInfo.InternalSetValue(PropertyInfo thisProperty, Object obj, Object value, Object[] index, StackCrawlMark& stackMark)
at System.Reflection.RuntimePropertyInfo.SetValue(Object obj, Object value, Object[] index)
我发现异常的来源是MainPage上的绑定,但并不真正理解为什么或导致它的原因。
由于
答案 0 :(得分:1)
您通过在usercontrol中明确设置DataContext
而丢失了DependencyProperty
。此外,您应该使用using System.Net;
using System.Windows;
using System.Windows.Controls;
namespace Client.Controls
{
public partial class CredentialsUserControl : UserControl
{
public CredentialsUserControl()
{
InitializeComponent();
if (System.ComponentModel.DesignerProperties.IsInDesignTool)
{
Credentials = new NetworkCredential("user","pass");
Title = "testing creds";
}
}
public ICredentials Credentials
{
get { return (ICredentials)GetValue(CredentialsProperty); }
set { SetValue(CredentialsProperty, value); }
}
// Using a DependencyProperty as the backing store for Credentials. This enables animation, styling, binding, etc...
public static readonly DependencyProperty CredentialsProperty =
DependencyProperty.Register("Credentials", typeof(ICredentials), typeof(CredentialsUserControl),new PropertyMetadata(null));
public string Title { get; set; }
}
}
。最后,您的XAML加载了Exact边距...您可能希望切换到使用网格行/列定义,就好像您需要更改页面一样,它会更容易。
<Grid Name="LayoutRoot">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<TextBlock Text="{Binding ElementName=control, Path=Title}" TextWrapping="Wrap" FontSize="30" Margin="12,24" />
<Grid Grid.Row="1" Margin="40,0,0,0">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="12" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<TextBlock Text="Username" FontSize="25" Grid.Column="0" />
<TextBlock Text="{Binding ElementName=control, Path=Credentials.User}" FontSize="25" Grid.Column="1" HorizontalAlignment="Right"/>
<TextBlock Text="Password" Grid.Row="2" FontSize="25" Grid.Column="0" />
<TextBlock Text="{Binding ElementName=control, Path=Credentials.Password}" Grid.Row="2" FontSize="25" Grid.Column="1" HorizontalAlignment="Right"/>
</Grid>
</Grid>
{{1}}
答案 1 :(得分:0)
我不确定,但构造函数中的代码块是什么:
LayoutRoot.DataContext = this;
this.DataContext = this;
看起来很“危险”......