How to: Specify the Binding Source

In data binding, the binding source object refers to the object you obtain your data from. This topic describes the different ways of specifying the binding source.

Example

If you are binding several properties to a common source, you want to use the DataContext property, which provides a convenient way to establish a scope within which all data-bound properties inherit a common source.

In the following example, the data context is established on the root element of the application. This allows all child elements to inherit that data context. Data for the binding comes from a custom data class, NetIncome, referenced directly through a mapping and given the resource key of incomeDataSource.

<Grid
 xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 x:Class="SDKSample.DirectionalBinding"
 xmlns:c="clr-namespace:SDKSample"
 Name="Page1"
>
 <Grid.Resources>
 <c:NetIncome x:Key="incomeDataSource"/>
 <Style TargetType="{x:Type TextBlock}">
 <Setter Property="Padding" Value="8"/>
 </Style>
 <Style TargetType="{x:Type TextBox}">
 <Setter Property="Margin" Value="0,6,0,0"/>
 </Style>
 </Grid.Resources>
 <Grid.DataContext>
 <Binding Source="{StaticResource incomeDataSource}"/>
 </Grid.DataContext>

</Grid>

The following example shows the definition of the NetIncome class.

public class NetIncome : INotifyPropertyChanged
{
 private int totalIncome = 5000;
 private int rent = 2000;
 private int food = 0;
 private int misc = 0;
 private int savings = 0;
 public NetIncome()
 {
 savings = totalIncome - (rent+food+misc);
 }

 public int TotalIncome
 {
 get
 {
 return totalIncome;
 }
 set
 {
 if( TotalIncome != value)
 {
 totalIncome = value;
 OnPropertyChanged("TotalIncome");
 }
 }
 }
 public int Rent
 {
 get
 {
 return rent;
 }
 set
 {
 if( Rent != value)
 {
 rent = value;
 OnPropertyChanged("Rent");
 UpdateSavings();
 }
 }
 }
 public int Food
 {
 get
 {
 return food;
 }
 set
 {
 if( Food != value)
 {
 food = value;
 OnPropertyChanged("Food");
 UpdateSavings();
 }
 }
 }
 public int Misc
 {
 get
 {
 return misc;
 }
 set
 {
 if( Misc != value)
 {
 misc = value;
 OnPropertyChanged("Misc");
 UpdateSavings();
 }
 }
 }
 public int Savings
 {
 get
 {
 return savings;
 }
 set
 {
 if( Savings != value)
 {
 savings = value;
 OnPropertyChanged("Savings");
 UpdateSavings();
 }
 }
 }

 private void UpdateSavings()
 {
 Savings = TotalIncome - (Rent+Misc+Food);
 if(Savings < 0)
 {}
 else if(Savings >= 0)
 {}
 }
 public event PropertyChangedEventHandler PropertyChanged;
 private void OnPropertyChanged(String info)
 {
 PropertyChangedEventHandler handler = PropertyChanged;
 if (handler !=null)
 {
 handler(this, new PropertyChangedEventArgs(info));
 }
 }
}

Public Class NetIncome
 Implements INotifyPropertyChanged

 ' Events
 Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged

 ' Methods
 Public Sub New()
 Me._totalIncome = 5000
 Me._rent = 2000
 Me._food = 0
 Me._misc = 0
 Me._savings = 0
 Me._savings = (Me.TotalIncome - ((Me.Rent + Me.Food) + Me.Misc))
 End Sub

 Private Sub OnPropertyChanged(ByVal info As String)
 RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(info))
 End Sub

 Private Sub UpdateSavings()
 Me.Savings = (Me.TotalIncome - ((Me.Rent + Me.Misc) + Me.Food))
 If ((Me.Savings >= 0) AndAlso (Me.Savings >= 0)) Then
 End If
 End Sub


 ' Properties
 Public Property Food As Integer
 Get
 Return Me._food
 End Get
 Set(ByVal value As Integer)
 If (Me.Food <> value) Then
 Me._food = value
 Me.OnPropertyChanged("Food")
 Me.UpdateSavings()
 End If
 End Set
 End Property

 Public Property Misc As Integer
 Get
 Return Me._misc
 End Get
 Set(ByVal value As Integer)
 If (Me.Misc <> value) Then
 Me._misc = value
 Me.OnPropertyChanged("Misc")
 Me.UpdateSavings()
 End If
 End Set
 End Property

 Public Property Rent As Integer
 Get
 Return Me._rent
 End Get
 Set(ByVal value As Integer)
 If (Me.Rent <> value) Then
 Me._rent = value
 Me.OnPropertyChanged("Rent")
 Me.UpdateSavings()
 End If
 End Set
 End Property

 Public Property Savings As Integer
 Get
 Return Me._savings
 End Get
 Set(ByVal value As Integer)
 If (Me.Savings <> value) Then
 Me._savings = value
 Me.OnPropertyChanged("Savings")
 Me.UpdateSavings()
 End If
 End Set
 End Property

 Public Property TotalIncome As Integer
 Get
 Return Me._totalIncome
 End Get
 Set(ByVal value As Integer)
 If (Me.TotalIncome <> value) Then
 Me._totalIncome = value
 Me.OnPropertyChanged("TotalIncome")
 End If
 End Set
 End Property


 ' Fields
 Private _food As Integer
 Private _misc As Integer
 Private _rent As Integer
 Private _savings As Integer
 Private _totalIncome As Integer
End Class

Alternatively, if you want to specify the source on your individual bindings explicitly, you have the following options. These take precedence over the inherited data context.

See also

• FrameworkElement.DataContext
• FrameworkContentElement.DataContext
• Property Value Inheritance
• Data Binding Overview
• Binding Declarations Overview
• How-to Topics