How to update the user interface when running long-time functions in WPF?

Question

In the form, I define a TextBlock object through XAML code and bind it to my custom attribute "Val". When running a long-time function, "Val" is constantly updated, but it is not updated to the form interface in real time. How to make the form interface update data in real time?（“ Val has implemented the INotifyPropertyChanged interface in its class.

...
<TextBlock Text="{Binding ElementName=myClass,Path=Val}"/>
...
...

.....
public int Val{
.....
}

public void LongTime(）{
    for(int i=0;i<10000000;i++){
           if(i%1000==0)
                 Val++;
     }
}
......

Answer 1

You can add a loop to your code, or DispatcherTimer to execute the LongTime. I will show you my demo with use a loop, if you want to use DispatcherTimer, you can refer to the answer.

The Xaml code :

 <Window.DataContext>  
        <local:ViewModel></local:ViewModel>  
    </Window.DataContext>  
    <Grid>  
        <TextBox Text="{Binding Val,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Width="200" Height="40" Background="Azure"/>  
    </Grid>  

The C# code is:

public class ViewModel : NotifyObject  
    {  
  
        public ViewModel()  
        {  
            Val = 0;  
            Thread thread = new Thread(LongTime);  
            thread.IsBackground = true;  
            thread.Start();  
        }  
  
        private int _Val;  
        public int Val  
        {  
            get  
            {  
                return _Val;  
            }  
            set  
            {  
                _Val = value;  
                OnPropertyChanged("Val");  
            }  
        }  
  
        public void LongTime()  
        {  
            int j = 0;  
  
            for (int i = 0; i < 10000000; i++)  
            {  
                while (j != 10000000)  
                {  
                    if (i % 1000 == 0)  
                    {  
                        Val++;  
                    }  
                    j++;  
                }  
            }  
        }  
    }  

The result pictire is:

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Answer 2

Hi,
you can use Task.Factory, see following code:

using System.ComponentModel;  
using System.Runtime.CompilerServices;  
using System.Threading.Tasks;  
using System.Windows;  
 
namespace WpfApp054  
{  
  public class myClass : FrameworkElement, INotifyPropertyChanged  
  {  
    public myClass() => Task.Factory.StartNew(() => LongTime());  
  
    private int _val;  
    public int Val { get => this._val; set { this._val = value; OnPropertyChanged(); } }  
  
    public void LongTime()  
    {  
      for (int i = 0; i < 10000000; i++)  
      {  
        if (i % 1000 == 0) Val++;  
        for (int k = 0; k < 10000; k++) { } // simulate working   
      }  
    }  
  
    public event PropertyChangedEventHandler PropertyChanged;  
    private void OnPropertyChanged([CallerMemberName] string propName = "") => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propName));  
  }  
}  

And XAML:

<Window x:Class="WpfApp1.Window054"  
        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:local="clr-namespace:WpfApp054"  
        mc:Ignorable="d"  
        Title="Long running method" Height="450" Width="800">  
  <StackPanel>  
    <local:myClass x:Name="myClass"/>  
    <TextBox Text="insert text to check non-blocking UI" />  
    <TextBox Text="{Binding ElementName=myClass, Path=Val}" />  
  </StackPanel>  
</Window>  

Result: