CODEWITHSUNDEEP
c#wpfmvvm
Vishal Chavan
Vishal Chavan

Reputation: 13

Update View when property value changed inside setter

I have checkbox in my view which has bound to the property in the viewmodel. When I check/uncheck the checkbox, there is one condition in setter of the property which updates the same property if the condition is true. But when the property gets updated corresponding view does not change.

Here is the code: View:

<CheckBox IsChecked="{Binding HoldingPen,Mode="Twoway" ,UpdateSourceTrigger=PropertyChanged}"/>

ViewModel:

public bool HoldingPen
{
  get{m_holdingPen;}
  set
  {
    m_hodingPen=value;
    onPropertyChanged("HoldingPen");
    OnHoldingPenCheckChanged();
  }

public void OnHoldingPenCheckChanged()
{
  if(HoldingPen && some other condition)
  {
    HoldingPen=false;  //Here view should be updated simultaneously 
  }
}

Upvotes: 1

Views: 556

Answers (1)

Rachel
Rachel

Reputation: 132588

I think it's a result of having two onPropertyChanged events fire, once with a value of true and one with a value of false

Typically for this kind of logic I prefer to use the PropertyChanged event instead of hiding the logic in property setters.

public class MyClass()
{
    public MyClass()
    {
        // attach property changed in constructor
        this.PropertyChanged += MyClass_PropertyChanged;
    }

    private void MyClass_PropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        if (e.PropertyName == "HoldingPen")
            OnHoldingPenCheckChanged();
    }

    public bool HoldingPen
    {
        get{ m_holdingPen; }
        set
        {
            if (m_hodingPen == value)
                return; 

            m_hodingPen=value;
            onPropertyChanged("HoldingPen");
        }
    }

    public void OnHoldingPenCheckChanged()
    {
        if(HoldingPen && some other condition)
        {
            HoldingPen=false;  //Here view should be updated simultaneously 
        }
    }
}

This has the additional benefit of having any custom code to modify a value in one location, rather than going through each setter when looking for something.

Upvotes: 1

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