How to make a label static

问题:

So I have a program in which I am telling the user whether two skeletons match, but the thing is that I need to access the label via a class. The error I keep getting is

Error1  An object reference is required for the
non-static field, method, or property 
'WpfApplication1.MainWindow.matchLabel'

Here's what I have in my code:

The static Label

static Label matching
    {
        get { return matchLabel; } //errors here
        set { matchLabel = value; } //and here
    }

The Class

private class Scan
    {
        private void Start()
        {
            Skeleton skeleton = new Skeleton();

            if (PersonDetected == true)
            {
                int SkeletonID2 = skeleton.TrackingId;

                if (SkeletonID1 == SkeletonID2)
                {
                    matching.Content = "Your IDs are Matching!";
                }

                else if (SkeletonID2 != SkeletonID1)
                {
                    matching.Content = "Your IDs don't Match.";
                }
            }
        }

        private void Stop()
        {
            if (PersonDetected == true)
            {
                matching.Content = "Scan Aborted";
            }
        }
    }

Basically I want to know how to make the label in wpf static, or if there is another way to do this.
Thanks in advance

回答1:

I think that you could use another approach, like @Daniel said, using UI elements on multiple threads is a bad idea.

If my understanding is correct, you just want to notify to the user the result from your domain logic, the way I would do it is simple, create an event:

public event Action<string> MyEvent = delegate { };

            if (SkeletonID1 == SkeletonID2)
            {
                this.MyEvent("Your IDs are Matching!");
            }

            else if (SkeletonID2 != SkeletonID1)
            {
                this.MyEvent("Your IDs don't Match.");
            }

 if (PersonDetected == true)
            {
                this.MyEvent("Scan Aborted");
            }

In your WPF view

this.MydomainComponent.MyEvent += (x) => { this.matchLabel.Content = x; };

回答2:

This is a bad idea. You shouldn't create UI elements on multiple threads.

You really should consider implementing the MVVM pattern. It will make your code more decoupled and increase testablility.

回答3:

Your best bet would be to use the built in WPF Databinding. You can use the MVVM pattern but it's not required for this to work.

Window Class (XAML)

<Window x:Class="WpfApplication2.MyWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MyWindow" Height="300" Width="300">
    <Grid>
        <Label Content="{Binding Path=MyLabelValue}" />
    </Grid>
</Window>

Window Code Behind (Code)

using System.Windows;
using System.ComponentModel;

namespace WpfApplication2
{
    /// <summary>
    /// Interaction logic for MyWindow.xaml
    /// </summary>
    public partial class MyWindow : Window, INotifyPropertyChanged
    {
        public MyWindow()
        {
            InitializeComponent();

            DataContext = this;  // Sets context of binding to the class 
        }


        // Property for binding
        private string _mylabelvalue;
        public string MyLabelValue
        {
            get { return _mylabelvalue; }
            set 
            { 
                _mylabelvalue = value;
                if(PropertyChanged != null)
                {
                    PropertyChanged(this, new PropertyChangedEventArgs("MyLabelValue"));
                }
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
    }
}

By using this method when you set / call the property on the window you get the value for the label. When you change the property - you update the value in the UI via data binding and the INotifyPropertyChanged interface. I have a section on doing this via reflection and using the MVVM pattern on my blog here.

http://tsells.wordpress.com/category/mvvm/