在WPF列表框中设置复选框项目的前景色

Question

I have several lists containing data from a db. The listboxes serves as filters for a chart, and the appearance of the listboxes should change depending on what is selected in other listboxes.

Here is a simplified example of what I'm trying to do specifically:

Class Region
{
public int RegionID { get; set; }
public string RegionName { get; set; }
}

Class Country
{
public int CountryID { get; set; }
public string CountryName { get; set; }
public int RegionID { get; set; }
}

private void fillListBoxes()
{
List<Region> allRegions = getRegions();
lstRegionsFilter.ItemsSource = allRegions;
}

A country obviously belongs to a region, and I also have for example Ports, which is then located in a country etc etc.

All listbox items are checkboxes defined like this:

<ListBox Name="lstRegionsFilter">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <CheckBox Content="{Binding Path=RegionName}"
                      Tag="{Binding Path=RegionID}" 
                      Click="CheckBox_Click"/>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

As items in any listbox is clicked they are added to a list of filters which will filter the data displaying the chart. So for example if "Europe" is selected under Regions then all Countries that belongs to Europe should be colored differently in the listbox for countries, for example blue.

So in code I want to loop through the check boxes in the country-listbox and set its foreground color to something depending on if the value displayed/tagged to that checkbox is a country that belongs to the selected Region so typically in a foreach loop. However the items in the listbox is of type Region so how can I access the underlying checkbox? This should be pretty basic stuff I know, but its driving me nuts!

Answer 1

Try this:

public class Region : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    private bool isChecked;

    private void OnPropertyChaned(string property)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(property));
    }

    public int RegionID { get; set; }
    public string RegionName { get; set; }

    public bool IsChecked
    {
        get { return isChecked; }
        set
        {
            if (isChecked != value)
            {
                isChecked = value;
                OnPropertyChaned("IsChecked");
            }
        }
    }
}

public class Country : INotifyPropertyChanged
{
    private readonly Region parentRegion;

    public event PropertyChangedEventHandler PropertyChanged;

    private void OnPropertyChanged(string property)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(property));
    }

    public Country(Region parent)
    {
        parentRegion = parent;
        parentRegion.PropertyChanged += ParentChanged;
    }

    private void ParentChanged(object sender, PropertyChangedEventArgs e)
    {
        if(e.PropertyName.Equals("IsChecked"))
        {
            OnPropertyChanged("IsParentChecked");
        }
    }

    public int CountryID { get; set; }
    public string CountryName { get; set; }
    public int RegionID { get { return parentRegion.RegionID; }}
    public bool IsParentChecked
    {
        get { return parentRegion.IsChecked; }
    }
}

and the xaml:

This is for the Regions:

<ListBox Name="lstRegionsFilter">
<ListBox.ItemTemplate>
    <DataTemplate>
        <CheckBox Content="{Binding Path=RegionName}"
                  Tag="{Binding Path=RegionID}"
                  IsChecked="{Binding Path=IsChecked}"
                  Click="CheckBox_Click"/>
    </DataTemplate>
</ListBox.ItemTemplate>
</ListBox>

And this is for the Countries

<ListBox Name="lstCountriesFilter">
<ListBox.ItemTemplate>
    <DataTemplate>
        <CheckBox ...
                  Foreground={Binding IsParentChecked, Converter={StaticResource boolToBrushConverter}"/>
                  ...
                  />
    </DataTemplate>
</ListBox.ItemTemplate>
</ListBox>

Note:

• You need to implement the Converter class (see here )
• Add the converter to the xaml as StaticResouce

The Country Checkboxes forecolor will change automatically if the regions IsChecked property changed (from the ui or from code-behind), so no loop needed.

I haven't tried it, probably you can find mistakes but I wanted to show the "phylosophy"

Hope it helps

Answer 2

If i get you right, your plan is to have a country highlighted in its region coulor if its region is selected ? Rq 1 : You don't have to loop through checkBoxes to know which region is selected : this is the purpose of the binding that the values of the binded collection themselves will be affected.
Rq2 : If you change the values in code, you have to implement INotifyPropertyChanged in your region class for the UI to be updated.
How to do it ?
1. have a static dictionnary of RegionId --> Boolean.
2. Whenever a RegionId gets selected/unselected, update that dictionnary and raise a static event 'SelectionDictionnaryUpdated'.
3. Now add a notifying property 'IsOwnerRegionSelected' in your Country class. it will look in the dictionnary to say if corresponding region is selected or not.
4. add property 'CountryRegionColor' in your Country class. It will return the color based on RegionId and, say a RegionId -> Color static dictionnary.
5. add a Trigger, inside your DataTemplate, and a DataTrigger that will switch color beetween white and CountryRegionColor, depending on IsOwnerRegionSelected value.
6. In the constructor of a country, add a handler to SelectionDictionnaryUpdated that will NotifyPropertyChanged on the "IsOwnerRegionSelected".

that's it !

1. you can make it with non-shared dictionnary (each country having a RegionId --> Boolean dictionnary property that you inject in constructor)
2. you can make things simpler by having 'CurrentCoulor': notifying property that will return either white or CountryRegionColor depending if it is selected or not. just bind the Background of your list to that property, and notifyCurrentCoulor changed when you catch SelectionDictionnaryUpdated.