CODEWITHSUNDEEP
.netwpfxamlcombobox
LTR
LTR

Reputation: 1372

Simple WPF ComboBox ItemsSource Binding doesn't work

I'm just getting started with WPF and Visual Studio 2010. When I try the following simple ComboBox binding, I get error messages.

XAML:

...
<ComboBox Height="23" HorizontalAlignment="Left" 
Margin="33,18,0,0" Name="comboBox1" VerticalAlignment="Top" Width="120" 
ItemsSource="{Binding Path=test}"/>
...

Code File:

public partial class SetupWindow2 : Window
{
    public List<string> test { get; set; }
    public SetupWindow2()
    {
        test = new List<string>() { "1", "2", "3" };
        InitializeComponent();
    }
}

Error Messages:

System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=test; DataItem=null; target element is 'ComboBox' (Name='comboBox1'); target property is 'ItemsSource' (type 'IEnumerable')
System.Windows.Data Information: 40 : BindingExpression path error: 'test' property not found for 'object' because data item is null.  This could happen because the data provider has not produced any data yet. BindingExpression:Path=test; DataItem=null; target element is 'ComboBox' (Name='comboBox1'); target property is 'ItemsSource' (type 'IEnumerable')
System.Windows.Data Information: 19 : BindingExpression cannot retrieve value due to missing information. BindingExpression:Path=test; DataItem=null; target element is 'ComboBox' (Name='comboBox1'); target property is 'ItemsSource' (type 'IEnumerable')
System.Windows.Data Information: 20 : BindingExpression cannot retrieve value from null data item. This could happen when binding is detached or when binding to a Nullable type that has no value. BindingExpression:Path=test; DataItem=null; target element is 'ComboBox' (Name='comboBox1'); target property is 'ItemsSource' (type 'IEnumerable')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=test; DataItem=null; target element is 'ComboBox' (Name='comboBox1'); target property is 'ItemsSource' (type 'IEnumerable')

Where is the problem here?

Upvotes: 2

Views: 6777

Answers (1)

blindmeis
blindmeis

Reputation: 22445

Whenever binding fails you should check the DataContext first and then the Binding expression.

In your case I would say the right datacontext is missing, so if your combobox is in your setupwindow2 you should add:

public partial class SetupWindow2 : Window
{
   public List<string> test { get; set; }

   public SetupWindow2()
   {
      test = new List<string>() { "1", "2", "3" };
      this.Datacontext = this;
   }
}

Upvotes: 4

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