C# Binding List to ComboBox

Question

I have a problem with my binding. Everything works except that the initial value displayed in the combo box of the selected is blank. The drop down has the two values below the blank that is originally display. Any help would be fantastic.

Main Class

public partial class MainWindow : Window
{
    public MainWindow()
   {
        InitializeComponent();
        public Data myData = new Data(new LocationSite("There", 9.81234));  
        Binding b = new Binding();
        b.Source = MainWindow.Data.Location;
        b.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;
        b.Path = new PropertyPath("Gravity");
        MainWindow.mainWindow.Gravity.SetBinding(TextBox.TextProperty, b);
        Binding b = new Binding() { Source = MainWindow.Data.LocationSelection };
        MainWindow.mainWindow.LocationComboBox.DisplayMemberPath = "Name";
        MainWindow.mainWindow.LocationComboBox.SetBinding(ComboBox.ItemsSourceProperty, b);
       //bind selection 
        MainWindow.mainWindow.LocationComboBox.DataContext = MainWindow.Data;
        Binding selectedItemBinding = new Binding() { Source = MainWindow.Data, Path = new PropertyPath("Location"), Mode = BindingMode.TwoWay} 
        MainWindow.mainWindow.LocationComboBox.SetBinding(ComboBox.SelectedValueProperty, selectedItemBinding);

        MainWindow.mainWindow.LocationComboBox.SelectedIndex = 0; // always index 0 but might need index 1 how do I make it use whatever location is?


}

}

Data class with a list of Locations and one location that is the selected. Somehow I need to tell the combo box that the one to select is the location that matched the list. Any Help????

public class Data : INotifyPropertyChanged
{
    private LocationSite location;
    private List<LocationSite> locationSelection;

    public Location(LocationSite useLocation)
    {
       location = useLocation; // can either be "Here" or "There" need start index either 0 or 1
       locationSelection = new List<LocationSite>();
       locationSelection.Add(new LocationSite("Here", 9.795884));
       locationSelection.Add(new LocationSite("There", 9.81234));

    }

    public LocationSite Location
    {
       get { return location; }
       set {
            if (location == null)
            {
              location = new LocationSite();
            }
            Location.Gravity = value.Gravity;
            Location.Name = value.Name;
          }
   }

/// <summary>
/// Getter/Setter of a list of LocationSites
/// </summary>
public List<LocationSite> LocationSelection
{
  get { return locationSelection; }
  set { locationSelection = value; }
}

public event PropertyChangedEventHandler PropertyChanged;

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

}

The object that I have a list of

public class LocationSite : INotifyPropertyChanged
  {
private string name;
private double gravity;

public LocationSite(string siteName, double siteGravity)
{
  Name = siteName;
  Gravity = siteGravity;
}
public string Name
{
  get { return name; }
  set { name = value;
  this.OnPropertyChanged("Name");
  }
}

public double Gravity
{
  get { return gravity; }
  set { gravity = value;
  this.OnPropertyChanged("Gravity");
  }
}
public event PropertyChangedEventHandler PropertyChanged;

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

 }
}

The XAML file

<Window x:Class="Data.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Needs to be updated" Height="820" Width="1280"  HorizontalAlignment="Left">
 <Grid Name="MainScreenGrid">

    <TextBox x:Name="Gravity" Grid.Column="8" HorizontalAlignment="Left" Height="23" Grid.Row="3" TextWrapping="NoWrap" Text="0.0" VerticalAlignment="Top" Width="140" IsHitTestVisible="False" IsReadOnly="True"/>
    <ComboBox x:Name="LocationComboBox" Grid.Column="6" HorizontalAlignment="Left" Grid.Row="1" VerticalAlignment="Top" Width="140" Height="22"/>
</Grid>
</Window>

Answer 1

In your Data Class Try this

private LocationSite location;

public LocationSite Location
{
   get 
      { 
        return location;
      }

   set 
      {
        location=value;
        OnPropertyChanged("Location")
      }
}

And in MainWindowConstructor Set the Value Like This

MainWindow.Data.Location=MainWindow.Data.LocationSelection.FirstOrDefault();

In this method By default It will Take the First Item of LocationSelection as Location. And You need to Use System.Linq NameSpace for FirstOrDefault().

Set the Location Value Before You Set the Binding.

Answer 2

in your constructor try this

LocationComboBox.SelectedIndex = 0;