将控件绑定到不同的DataContext

Question

I have a situation where I want to bind a ListBox with a List of class items and SolidColorBrush property to foreground of a TextBlock that is part of the ListBox itself.

Data of ListBox comes from the class User and SolidColorBrush property from the class MyColors However, I am not able to set DataContexts for both of them at the same time. Setting DataContext twice overrides the first one and the ListBox is not populated. Please help!

public Page1()
    {
        this.DataContext = GetUsers();
        this.DataContext = textcolor; // <-overrides the previous DataContext
    }

Code Behind:

xaml:

<Grid HorizontalAlignment="Left" Height="650" Margin="0,38,0,0" Grid.RowSpan="2" VerticalAlignment="Top" Width="480">
        <ListBox x:Name="lstBani1" ItemsSource="{Binding}" >
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <StackPanel Orientation="Vertical">
                        <TextBlock x:Name="tb1" Text="{Binding string1}" Foreground="{Binding Path=Brush1, Mode=OneWay}" Width="480"/>
                        <TextBlock x:Name="tb2" Text="{Binding string2}" Width="480"/>
                        <TextBlock x:Name="tb3" Text="{Binding string3}" Width="480"/>
                    </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </Grid>

cs:

 public partial class Page1 : PhoneApplicationPage
    {
        public Page1()
        {
            InitializeComponent();          
            MyColors textcolor = new MyColors();
            textcolor.Brush1 = new SolidColorBrush(Colors.Red);

            this.DataContext = GetUsers();
            this.DataContext = textcolor; // <-overrides the previous DataContext
        }
        private List<User> GetUsers() {...}
    }   
    public class User
        {
            public string string1 { get; set; }
            public string string2 { get; set; }
            public string string3 { get; set; }
        } 


public class MyColors : INotifyPropertyChanged
    {
        private SolidColorBrush _Brush1;
        public event PropertyChangedEventHandler PropertyChanged;

        public SolidColorBrush Brush1
        {
            get { return _Brush1; }
            set
            {
                _Brush1 = value;
                NotifyPropertyChanged("Brush1");
            }
        }

        public void NotifyPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this,
                    new PropertyChangedEventArgs(propertyName));
            }
        }
    }

Answer 1

there are a quite a few ways to achieve this.

Though as my time at the desk here is limited tonight I'll do it in a bit of a messy ViewModel type way.

Rather than trying to pass two objects into the datacontext. What I would suggest is creating what is commonly called a View Model. If you aren't familiar with the MVVM pattern, there's quite a lot on-line to read up on. It's a large pattern however and I only use small parts of it for most of my work.

Based on your code from above, I have added a class which looks something like the following.

public class AViewModel
{
    public List<User> Users { get; set; }
    public MyColors Colours { get; set; }
}

This is the object I'm going to pass as the data context, and newing up the list of Users and MyColors before passing it to the datacontext.

Now, for the list box I can do something like this...

<ListBox ItemsSource="{Binding Users}" Foreground="{Binding Colours.Brush1}">

        <ListBox.ItemTemplate>
            <DataTemplate>
                <StackPanel Orientation="Vertical">
                    <TextBlock x:Name="tb1" Text="{Binding string1}" Foreground="{Binding Foreground, RelativeSource={RelativeSource Mode=TemplatedParent}}" Width="480"/>
                </StackPanel>
            </DataTemplate>
        </ListBox.ItemTemplate>

    </ListBox>

I bind the foreground of the Listbox to the colour, and then pass that using relative source on the TextBlocks's Foreground DP

I did this with a Windows UNI app and I have red text showing in my items. However, there are numerous things which could override this colour. And we could go on all night talking about that.

Hope this is of some help to you.