WPF User Control Not Data Binding

Question

In my user control I have a dependency property that is not data binding. I have looked over several stack overflow posts and I cannot figure out what I am doing wrong. The Property changed method is never called. My Code so far:

My user control is basically a enhanced combo box. The DP lives inside of the user control. I am using this user control inside of a Data Grid.

The data context of the user control is set like this. DataContext={Binding RelativeSource={RelativeSource Self}}

#region ProfileType DP

    public static FrameworkPropertyMetadata ProfileTypeMetaData = new FrameworkPropertyMetadata(ProfileTypes.Default,
                                                                 FrameworkPropertyMetadataOptions.BindsTwoWayByDefault |
                                                                FrameworkPropertyMetadataOptions.Journal, new PropertyChangedCallback(ProfileType_PropertyChanged),
                                                                new CoerceValueCallback(ProfileType_CoerceValue),
                                                                false, UpdateSourceTrigger.PropertyChanged);

    public static readonly DependencyProperty ProfileTypeProperty = DependencyProperty.Register(nameof(ProfileType), typeof(ProfileTypes),
                                                                  typeof(MyClass), ProfileTypeMetaData, new ValidateValueCallback(ProfileType_Validate));

    private static void ProfileType_PropertyChanged(DependencyObject dobj, DependencyPropertyChangedEventArgs e)
    {
        MyClass tp = (MyClass)dobj;
        tp.SetUpProfiles();
    }

    private static object ProfileType_CoerceValue(DependencyObject dobj, object Value)
    {
        return Value;
    }

    private static bool ProfileType_Validate(object Value)
    {
        return true;
    }

    public ProfileTypes ProfileType
    {
        get
        {
            return (ProfileTypes)this.GetValue(ProfileTypeProperty);
        }
        set
        {
            this.SetValue(ProfileTypeProperty, value);
        }
    }

    #endregion

In my xaml file I have the following:

<DataGrid ItemsSource="{Binding Missmatches}" CanUserAddRows="False" AutoGenerateColumns="False">
   <DataGrid.Columns>
      <DataGridTextColumn Header="Target Profile" Binding="{Binding OldProfile}" />
          <DataGridTemplateColumn Header="Mismatched Profile">
             <DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <Tekla:TeklaProfiles SelectedProfile="{Binding NewProfile}" ProfileType="{Binding Type}" />
                  </DataTemplate>
              </DataGridTemplateColumn.CellTemplate>
           </DataGridTemplateColumn>
    </DataGrid.Columns>
</DataGrid>

The DataGrid is bound to an ObservableCollection. Each object in the collection contains three auto props.

private ObservableCollection<ProfileMismatch> _missmatches;
        public ObservableCollection<ProfileMismatch> Missmatches
        {
            get { return _missmatches; }
            set
            {
                if (_missmatches == value)
                    return;
                _missmatches = value;
                RaisePropertyChanged(nameof(Missmatches));
            }
        }

No matter what I try I cannot seem to get the user control to data bind. If any one has some pro tips please let me know.

Answer 1

The data context of the user control is set like this. DataContext={Binding RelativeSource={RelativeSource Self}}

Remove that. Explicitly setting a UserControl's DataContext prevents inheriting a DataContext from the control's parent, e.g. here:

<DataTemplate>
    <Tekla:TeklaProfiles SelectedProfile="{Binding NewProfile}"
                         ProfileType="{Binding Type}" />
</DataTemplate>

The bindings are expected to be resolved against the current DataContext, i.e. a view model object with a NewProfile and Type property. However, since you've explicitly set the DataContext of the UserControl (to itself), it won't work.

---

So just don't explicitly set a UserControl's DataContext. Never. Any blogs or online tutorials telling you so are plain wrong.