Question

当我通过XAML将我的按钮连接到命令时，我得到了运行时错误 System.Windows.Markup.XamlParseException：在System.Windows.Data.Binding＆＃39;上提供值。抛出一个例外。 ---＆GT; System.InvalidCastException：无法转换类型为＆＃39; System.Reflection.RuntimeEventInfo＆＃39;的对象输入＆＃39; System.Reflection.MethodInfo＆＃39;。

当我在XAML中删除命令绑定时，一切正常，我的项目显示等等。这是命令绑定：

Click="{Binding ElementName=MainGrid, Path=DataContext.AlertClickCommand}"

连接视图模型的代码（在我窗口后面的代码中）：

this.AlertsView.DataContext = GlobalStuff.AlertManager1.AlertViewModel1;

以下是我的视图模型我的视图模型是我视图的数据上下文

using System.Collections.Generic;
using System.ComponentModel;
using Arkle.SharedUI.Model;
using Arkle.SharedUI.ViewModel.Commands;

namespace Arkle.SharedUI.ViewModel
{
    public class AlertViewModel : INotifyPropertyChanged
    {

        private List<Alert> _alerts = new List<Alert>();
        public List<Alert> Alerts
        {
            get { return _alerts; }
            set
            {
                _alerts = value;
                OnPropertyChanged("Alerts");
            }
        }


        public AlertViewModel()
        {
            if (DesignerProperties.IsInDesignMode)
            {
                LoadDesignTimeData();
            }
        }

        private void LoadDesignTimeData()
        {
            Alerts.Add(new Alert { BackgroundMessage = "Sis", IsAlerting = true, OverlayMessage = "3 mins", Tip = "Sis Data not received for 3 mins" });
            Alerts.Add(new Alert { BackgroundMessage = "Bets", IsAlerting = true, OverlayMessage = "4", Tip = "4 unchecked danger bets" });
            Alerts.Add(new Alert { BackgroundMessage = "Texts", IsAlerting = false, OverlayMessage = "3", Tip = "3 Unchecked Text Bets" });
        }

        private AlertClickCommand _alertClickCommand;
        public AlertClickCommand AlertClickCommand
        {
            get { return _alertClickCommand ?? (_alertClickCommand = new AlertClickCommand(this)); }
        }
        public event PropertyChangedEventHandler PropertyChanged;

        protected virtual void OnPropertyChanged(string propertyName)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

这是我的xaml

<UserControl x:Class="Arkle.SharedUI.View.AlertsView"
    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"
        xmlns:viewModel="clr-namespace:Arkle.SharedUI.ViewModel"
        mc:Ignorable="d"
        d:DataContext="{d:DesignInstance Type=viewModel:AlertViewModel, IsDesignTimeCreatable=True}"
        x:Name="EarlyPriceEditorViewModelWindow"
    Height="Auto" Width="Auto">
    <UserControl.Resources>
        <BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter"/>
    </UserControl.Resources>

    <Grid Name="MainGrid">
        <StackPanel Name="MainStackPanel">
            <ListBox   ItemsSource="{Binding Path=Alerts}"   >
                <ListBox.ItemsPanel>
                    <ItemsPanelTemplate>
                        <WrapPanel Orientation="Horizontal" >
                        </WrapPanel>
                    </ItemsPanelTemplate>
                </ListBox.ItemsPanel>

                <ListBox.ItemTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Horizontal" Visibility="{Binding IsAlerting,Converter={StaticResource BooleanToVisibilityConverter}}">
                            <StackPanel Orientation="Horizontal">
                                <Button Content="{Binding BackgroundMessage}" HorizontalAlignment="Left"  Width="75"  VerticalAlignment="Top" Height="Auto"  Margin="2" 
                                    Click="{Binding ElementName=MainGrid, Path=DataContext.AlertClickCommand}" CommandParameter="{Binding}"

                                 />
                                <Label Content="{Binding OverlayMessage}" HorizontalAlignment="Left" Width="Auto" Margin="1,0,0,0" VerticalAlignment="Top" Background="Red" Foreground="White"
                                   FontWeight="Bold">
                                    <Label.Style>
                                        <Style>
                                            <Style.Triggers>
                                                <DataTrigger Binding="{Binding IsAlerting}" Value="True">
                                                    <Setter  Property="Image.Visibility" Value="Visible" />
                                                    <DataTrigger.EnterActions>
                                                        <BeginStoryboard x:Name="ImageFlash">
                                                            <Storyboard>
                                                                <DoubleAnimation Storyboard.TargetProperty="(UIElement.Opacity)"
                                                BeginTime="0:0:0" Duration="0:0:0.5"
                                                From="1.0" To="0.0" RepeatBehavior="Forever" AutoReverse="True"/>
                                                            </Storyboard>
                                                        </BeginStoryboard>
                                                    </DataTrigger.EnterActions>
                                                    <DataTrigger.ExitActions>
                                                        <StopStoryboard BeginStoryboardName="ImageFlash" />
                                                    </DataTrigger.ExitActions>
                                                </DataTrigger>
                                                <DataTrigger Binding="{Binding IsAlerting}" Value="False">
                                                    <DataTrigger.Setters>
                                                        <Setter  Property="Image.Visibility" Value="Collapsed" />
                                                    </DataTrigger.Setters>
                                                </DataTrigger>
                                            </Style.Triggers>
                                        </Style>

                                    </Label.Style>
                                </Label>
                                <Label Content="|" Margin="5"/>
                            </StackPanel>


                        </StackPanel>
                    </DataTemplate>
                </ListBox.ItemTemplate>

            </ListBox>


        </StackPanel>
    </Grid>

</UserControl>

这是我的命令

using System;
using System.Windows.Input;
using Arkle.Common;
using Arkle.SharedUI.Events;
using Arkle.SharedUI.Model;

namespace Arkle.SharedUI.ViewModel.Commands
{
    public class AlertClickCommand : ICommand
    {
        private AlertViewModel _alertViewModel;
        public AlertClickCommand(AlertViewModel alertViewModel)
        {
            _alertViewModel = alertViewModel;
        }

        public void Execute(object parameter)
        {
            if (parameter == null)
            {
                return;
            }
            var parameterAsAlert = (Alert)parameter;

            switch (parameterAsAlert.BackgroundMessage)
            {
                case "Bets":
                    EventManager.Instance.GetEvent<ShowDangerBetsRequestedEvent>().Publish(null);
                    break;
                default:
                    return;
            }
        }

        public bool CanExecute(object parameter)
        {
            return true;
        }

        public event EventHandler CanExecuteChanged;
    }
}

我还得到以下设计时错误（见截图）无法转换类型为＃System; Winds.Data.Binding＆＃39;的对象。键入＆＃39; Microsoft.Expression.Markup.DocumentModel.DocumentNode＆＃39;。

enter image description here

首次运行时错误 - 投掷 enter image description here

后续运行时错误重复抛出： System.Windows.Markup.XamlParseException：在System.Windows.Data.Binding＆＃39;上提供值。抛出一个例外。 ---＆GT; System.InvalidCastException：无法转换类型为＆＃39; System.Reflection.RuntimeEventInfo＆＃39;的对象输入＆＃39; System.Reflection.MethodInfo＆＃39;。

在MS.Internal.Helper.CheckCanReceiveMarkupExtension（MarkupExtension markupExtension，IServiceProvider serviceProvider，DependencyObject＆amp; targetDependencyObject，DependencyProperty＆amp; targetDependencyProperty）

在System.Windows.Data.BindingBase.ProvideValue（IServiceProvider serviceProvider）

在MS.Internal.Xaml.Runtime.ClrObjectRuntime.CallProvideValue（MarkupExtension me，IServiceProvider serviceProvider）

---内部异常堆栈跟踪结束---

在System.Windows.FrameworkTemplate.LoadTemplateXaml（XamlReader templateReader，XamlObjectWriter currentWriter）

.......................

Answer 1

您不会将命令绑定到Click属性。 Click属性用于向Click事件添加传统事件处理程序。您希望使用Command属性来绑定命令。

<Button Content="{Binding BackgroundMessage}" 
        HorizontalAlignment="Left"  Width="75"  
        VerticalAlignment="Top" Height="Auto"  Margin="2" 
        Command="{Binding ElementName=MainGrid, 
                          Path=DataContext.AlertClickCommand}" 
        CommandParameter="{Binding}" />

Answer 2

如何更改此XAML：

<Button Content="{Binding BackgroundMessage}" 
        HorizontalAlignment="Left"  Width="75"  
        VerticalAlignment="Top" Height="Auto"  Margin="2" 
        Click="{Binding ElementName=MainGrid,                
                        Path=DataContext.AlertClickCommand}" 
        CommandParameter="{Binding}" />

到此：

<Button Content="{Binding BackgroundMessage}" 
        HorizontalAlignment="Left"  Width="75"  
        VerticalAlignment="Top" Height="Auto"  Margin="2" 
        Command="{Binding ElementName=MainGrid,                         
                          Path=DataContext.AlertClickCommand}" 
        CommandParameter="{Binding}" />

命令绑定无法将“System.Reflection.RuntimeEventInfo”类型的对象强制转换为“System.Reflection.MethodInfo”类型

2 个答案: