Bind DoubleUpDown Value after Minimum and Maximum

Question

I have a UserControl with a ListBox and a DoubleUpDown. When I select the item in the ListBox I want to set the Minimum, Maximum and the Value of the DoubleUpDown so the user can change the Value not from predefined range, but in some range around the given value. I use this code:

<extToolkit:DoubleUpDown Increment="0.1" Value="{Binding SelectedItem.MyValue, ElementName=listBox1, UpdateSourceTrigger=PropertyChanged, Converter={conv:CheckValue}}" FormatString="0.0">
    <extToolkit:DoubleUpDown.Maximum>
        <MultiBinding Converter="{conv:CorMaximum}">
            <Binding Path="SelectedItem.MyValue" ElementName="listBox1" />
            <Binding Path="SelectedItem.MaxDif" ElementName="listBox1" />
        </MultiBinding>
    </extToolkit:DoubleUpDown.Maximum>
    <extToolkit:DoubleUpDown.Minimum>
        <MultiBinding Converter="{conv:CorMinimum}">
            <Binding Path="SelectedItem.MyValue" ElementName="listBox1" />
            <Binding Path="SelectedItem.MaxDif" ElementName="listBox1" />
        </MultiBinding>
    </extToolkit:DoubleUpDown.Minimum>
</extToolkit:DoubleUpDown>

The problem is that this code first set the Value and after that set the Minimum and Maximum so if I have this values:

Name | MyValue | MaxDif
-----------------------
 One |    6    |   2
 Two |    1    |   1

The range for One is 4..8 and the range for Two is 0..2. If I first select One and then Two it looks like the Two.MyVal = 4, because the value is inserted when the range from One is still active.

How to change the code to first set the Minimum and Maximum and after that set the Value?

I'm not 100% sure if that is really the case, but from my observation the order in which the properties are set in XAML determines how they are initialized/assigned. Try binding the Value **after** Max/Min like e.g.: ` — Manfred Radlwimmer, Oct 03 '17 at 08:01
Yes, you are right. I just hope that this really works 100% of time :-) — Artholl, Oct 03 '17 at 08:13

Manfred Radlwimmer · Accepted Answer · 2017-10-03T08:36:41.320

Official Design Recommendations state

Allow properties to be set in any order even if this results in a temporary invalid state of the object

Which basically means when designing your own control, make sure to omit sanity checks until initialization is complete (until IsInitialized is true and the Initialized event is fired).

Apparently the DoubleUpDown was not designed with your exact problem in mind and enforces Min/Max boundaries before initialization is complete.

Edit: The public source code of this particular control seems to take IsInitialized into account so the problem you are having shouldn't actually occur.

While it is not explicitly stated in any documentation I was able to find, the Xaml Parser sets an objects properties in the order they are encountered.

Possible Solution:

You should be able to work around this problem by setting the Value property last.

Bind DoubleUpDown Value after Minimum and Maximum

1 Answers1