Array value binding in WPF

Question

I have an object with an Array of doubles property like this:

private double[] _axes;

public double[] Axes
{
    get
    {
        return _axes;
    }
    set
    {
        _axes = value;
        if (PropertyChanged != null)
        {
            NotifyPropertyChanged("Axes[]");
        }
    }
}

This Array is always assigned as a whole, because i get an Array of double out of my database object and set it to the Axes property like this:

object.Axes = GetDataRow(i);

(this is just to demonstrate that i in fact assign the whole Array)

In my XAML now i bind it like this:

 <Label  Content="{Binding Path=Axes[0], UpdateSourceTrigger=PropertyChanged}"

I set the DataContext of the window to the Object that has the Axes property and the UI receives one value from it at program start that i assign in the constructor of the object. However, even though the "Axes[]" event is raised constantly (which i checked from another object), no further values arrive in the UI.

So my question is: CAN this even work? Does Axes[] not correspond to Axes[0]? what could be the problem?

Praveen Paulose · Accepted Answer · 2015-04-17 16:26:21Z

2

Your property name is incorrect in the notification

if (PropertyChanged != null)
{
     NotifyPropertyChanged("Axes");
}

Remove the brackets. This should solve your problem in this case. However, it is recommended to use ObservableCollection for binding a list of objects.

edited Apr 17, 2015 at 16:26

answered Apr 17, 2015 at 16:10

Praveen Paulose

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5 Comments

SLaks Over a year ago

That won't help if he mutates the array

Praveen Paulose Over a year ago

@Anoobi If it answers your query, do not forget to mark it as the answer.

Praveen Paulose Over a year ago

@SLaks What does it mean to mutate the array?

SLaks Over a year ago

@PraveenPaulose: Axes[2] = 4;

Praveen Paulose Over a year ago

@SLaks agreed. His question explicitly stated he replaces the entire array. Thats why the Array solution

Tim · Accepted Answer · 2015-04-17 16:12:46Z

0

The binding system won't look "into" the array for updates. You just need to notify it that the property itself changed. You're currently saying that a property called Axes[] changed, but you don't have a property with that name. It's just Axes

public double[] Axes
{
    get
    {
        return _axes;
    }
    set
    {
        _axes = value;
        if (PropertyChanged != null)
        {
            NotifyPropertyChanged("Axes");
        }
    }
}

If you really need to know if an individual item in the array is changing, then you should be using ObservableCollection, which the binding system does know how to look "into".

answered Apr 17, 2015 at 16:12

Tim

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Comments

SLaks · Accepted Answer · 2015-04-17 16:10:31Z

0

No.

You have no property named Axes[], so that event has no effect.

You should not bind to arrays; instead, use ObservableCollection, and make the property read-only.

answered Apr 17, 2015 at 16:10

SLaks

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