视觉工作室 WPF C# | OnPropertyChange | 不清楚的行为

Question

I'm working on a plugin that I didn't start developing and there is a behaviour that I don't understand.

Code:

MAINWINDOW.xaml

TABLE1 and TABLE2 structures

<DataGrid ...>
   ...
   <DataGridTemplateColumn Header="title" Width="Auto">
      <DataGridTemplateColumn.CellTemplate>
         <DataTemplate>
            <TextBox Text="{Binding Path=MYPROPERTY, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
         </DataTemplate>
      </DataGridTemplateColumn.CellTemplate>
   </DataGridTemplateColumn>
   ...
</DatGrid>

MAINWINDOW.xaml.cs

      private void MYCLASS_Changed(object sender, EventArgs e)
      {
LineY    if (!_isInitialising) { Recalculate(); }
      }

OTHER C# FILE

namespace NAME
{
   public class MYCLASS : INotifyPropertyChanged
   {
      ...
      public event PropertyChangedEventHandler PropertyChanged;
      ...
      public double MYPROPERTY
      {
         get {...}
         set {...; OnPropertyChanged("MYPROPERTY");}
      }
      ...
      public void OnPropertyChanged(string name)
      {
         PropertyChangedEventHandler handler = PropertyChanged;
         if (handler != null)
         {
LineX       handler(this, new PropertyChangedEventArgs(name));
         }
      }
   }
}

Behaviour: I have a first table TABLE1 in MAINWINDOW.xaml. When I change MYPROPERTY in TABLE1 it calls the OnPropertyChange (LineX) and then jumps to VOID MYCLASS_CHANGED in MAINWINDOW.xaml.cs (LineY) and I don't undertand why this link happens, is someone able to explain it or tell me what to look when debugging (I'm not an actual programmer)?

I have a second table TABLE2 in MAINWINDOW.xaml. When I change MYPROPERTY in TABLE2 it calls the OnPropertyChange but it doesn't jump to the other function. I would like to in order to call some functions inside MAINWINDOW.xaml.cs

Answer 1

Your code appears to be structured as Model - View - ViewModel pattern (MVVM).

Your ViewModel cannot/should not access the View directly hence the use of Binding this instructs the .NET framework to expect an event trigger in which the new value of the bound parameter is sent - this is the PropertyChangedEvent . If declared "OneWay" then this is from the ViewModel to the View, if "BothWays" then entry of data on the View will trigger a change within the ViewModel property.

MainWindow.xaml and MainWindow.xaml.cs jointly make up the View (hence the partial declaration within MainWindow.xaml.cs).

MainWindow.xaml.cs is what is referred to as the "code behind" file for MainWindow.xaml.

In MVVM the View displays data that has been presented/retrieved/calculated by the ViewModel which in turn gets its base data structure from the Model.

There is some overlap in function, often you will see no Model (all of the data being held within the ViewModel) or some business logic within the code behind file (rather than just within the ViewModel).

It would appear that, in your code, you have the OnPropertyChangedEvent from the ViewModel triggering the MYCLASS_Changed event handler within your code behind file.

I suspect that this is related to your data trigger set by UpdateSourceTrigger=PropertyChanged but can't say for certain with the code that you have posted.