CODEWITHSUNDEEP
wpfwindows
Wtf1sh
Wtf1sh

Reputation: 137

How to set DataContext with binding?

I have a DockPanel set up like this

<Window ... >
<DockPanel x:Name="myDock" DataContext="{Binding HonapokList}" >

Inside the Dockpanel there is a TextBox, like this

<TextBox x:Name="tbCount" Text="{Binding Path=Count,Mode=OneWay}" />
</DockPanel>   
</Window>

This is how i set up HonapokList, so it's basically a List String>

public List<String> HonapokList;
    public MainWindow()
    {
        InitializeComponent();
        HonapokList = new List<string>();           
        Honapok.ItemsSource = HonapokList;
        HonapokList.Add("January");
        HonapokList.Add("February");
        HonapokList.Add("March");
    }

I want my textbox to display the number of elements in the HonapokList ( 3 in this example), however nothing is in it. Why is that?

Upvotes: 2

Views: 1186

Answers (2)

Rohit Vats
Rohit Vats

Reputation: 81233

First of all you can bind with Properties only and not with fields. So, make HonapokList a property -

public List<String> HonapokList { get; }

Secondly, change your xaml to look up for the property in your Window class using RelativeSource-

<DockPanel x:Name="myDock">
   <TextBox x:Name="tbCount"
            Text="{Binding Path=HonapokList.Count, Mode=OneWay,
                           RelativeSource={RelativeSource Mode=FindAncestor, 
                                                    AncestorType=Window}}"/>
</DockPanel>

OR

Set the DataContext on your window

<Window DataContext="{Binding RelativeSource={RelativeSource Self}}">

and then you can do like this -

<TextBox x:Name="tbCount"
         Text="{Binding Path=HonapokList.Count, Mode=OneWay}"/>

Upvotes: 1

John Bowen
John Bowen

Reputation: 24453

Window doesn't have a default DataContext, but it looks like you're assuming it to be set to itself. You can set it to do that either in the constructor:

DataContext = this;

or in the XAML:

<Window DataContext="{Binding RelativeSource={RelativeSource Self}}">

You're also going to need to change HonapokList to be a property, not a field as it is now, in order to bind to it.

Upvotes: 5

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