MVVM模式:BindingExpression路径错误:在“对象"上找不到“数据"属性 [英] MVVM Patttern: BindingExpression path error: 'Data' property not found on 'object'

问题描述

我正在尝试(第一次)使用MVVM模式使WPF图表工作，但我不明白该问题！为什么在调试时在MainWindow上什么也看不到！在我的输出窗口中，我收到以下错误消息:

System.Windows.Data错误:40:BindingExpression路径错误:在>''object''''''String''(HashCode = -354185577)''上找不到``Data''属性. BindingExpression:Path =数据; DataItem =''字符串''(HashCode = -354185577);目标元素是``ColumnSeries''(Name ='''');目标属性是>''ItemsSource''(类型``IEnumerable'')

这是myProject.View
中的mainwindow.xaml

I''m trying to use (for the first time) MVVM pattern to make a WPF chart work and I can''t understand the problem! why I get nothing on my MainWindow while debugging ! in my output window i have this error message:

System.Windows.Data Error: 40 : BindingExpression path error: ''Data'' property not found on >''object'' ''''String'' (HashCode=-354185577)''. BindingExpression:Path=Data; DataItem=''String'' (HashCode=-354185577); target element is ''ColumnSeries'' (Name=''''); target property is >''ItemsSource'' (type ''IEnumerable'')

here is my mainwindow.xaml in myProject.View

<Window x:Class="Chart.MainWindow"

    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

    xmlns:chartingToolkit="clr-namespace:System.Windows.Controls.DataVisualization.Charting;assembly=System.Windows.Controls.DataVisualization.Toolkit"

     xmlns:diag="clr-namespace:System.Diagnostics;assembly=WindowsBase"

    Title="MainWindow" Height="350" Width="525"

    DataContext="Test">
<Grid>
    <chartingToolkit:Chart 

        Height="262" 

        HorizontalAlignment="Left" 

        Margin="33,0,0,620"

        Name="columnChart" 

        Title="ColumnSeriesDemo"

        VerticalAlignment="Bottom"

        Width="360">
              <chartingToolkit:ColumnSeries 

                  IndependentValueBinding="{Binding Path=DateTest, diag:PresentationTraceSources.TraceLevel=High}"

                  DependentValueBinding="{Binding Path=VolumeTest ,diag:PresentationTraceSources.TraceLevel=High}"

                  ItemsSource="{Binding Path=Data, Mode=TwoWay, diag:PresentationTraceSources.TraceLevel=High}" />
    </chartingToolkit:Chart>
</Grid>
</Window>

这是我的mainwindow.xaml

and here is my mainwindow.xaml

namespace Chart
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
    private BindingVM Test;
    public MainWindow()
    {  
        this.Test = new BindingVM();   
        this.DataContext = Test;

        InitializeComponent();   
    }
}
}

这是myProject.ModelView中的ModelView类.

here is my ModelView class in myProject.ModelView

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections.ObjectModel;
using Chart.Model;
using System.Windows.Threading;
using System.ComponentModel;

namespace Chart.ViewModel
{
class BindingVM
{
    public BindingVM()
    {

       // AddElement();
        timer.Tick += new EventHandler(timer_Tick);
        timer.Interval = TimeSpan.FromSeconds(1);
        timer.Start();

    }

    DataItem item = new DataItem();
    public DateTime DateTest
    {
        get { return item.date; }
        set { item.date = value;
              propChanged("date");
            }
    }

    public Double VolumeTest
    {
        get { return item.volume; }
        set
        {
            item.volume = value;
            propChanged("volume");
        }
    }
    public DispatcherTimer timer = new DispatcherTimer();

    public event PropertyChangedEventHandler PropertyChanged;
    public void propChanged(String propname)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propname));
        }
    }

   public ObservableCollection<DataItem> DataTest = new ObservableCollection<DataItem>();
   public ObservableCollection<DataItem> Data
   {
       get { return DataTest;}
       set { DataTest= value;
             propChanged("data");
           }
   }



   public void timer_Tick(object sender, EventArgs e)

    {
        Random rnd = new Random();
        double baseValue = 20 + rnd.NextDouble() * 10;
        double value = baseValue + rnd.NextDouble() * 6 - 3;

        DataTest.Add(new DataItem()
        {
            date = DateTime.Now,
            open = value + rnd.NextDouble() * 4 - 2,
            high = value + 2 + rnd.NextDouble() * 3,
            low = value - 2 - rnd.NextDouble() * 3,
            close = value + rnd.NextDouble() * 4 - 2,
            volume = rnd.NextDouble() * 200,

        });

        baseValue = value < 6 ? value + rnd.NextDouble() * 3 : value;



        // DataTest.RemoveAt(0);
    }
 }
}

这是我在myProject.Model
中的模型

here is my model in myProject.Model

<pre lang="c#">using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Chart.Model
{
public class DataItem
{
    public DateTime date { get; set; }
    public double open { get; set; }
    public double high { get; set; }
    public double low { get; set; }
    public double close { get; set; }
    public double volume { get; set; }
}

}

任何想法为什么它不起作用??? !!

Any ideas why it doesn''t work ???!!

推荐答案

您可以在xaml中设置MainWindow 的DataContext.

在mainwindow.xaml中删除此行:

DataContext="Test"

这应该可以解决.

You set the DataContext of the MainWindow in xaml.

Remove this line in mainwindow.xaml:

DataContext="Test"

This should solve it.

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