Binding Directions in WPF.

We are using different binding modes for populating the value in to the UI.

We can set the values using Mode property of binding. The values are available in  System.Windows.Data.BindingMode enumeration.

Values of Binding Mode Enumeration

OneWay

The target property is updated only when the source property changes.

<TextBlock Text="{Binding firstname , Mode=OneWay}"></TextBlock>

TwoWay                                                                                     

The target property is updated only when the source property changes and the source property is changed/Updated when the target property is changed.

<TextBlock Text="{Binding firstname , Mode=TwoWay}"></TextBlock>
OneTime

The target property set initially based on the Source property value. However, changes are ignored from that point onword.Usually we can use this mode to reduce the overhead.

<TextBlock Text="{Binding firstname , Mode=OneTime}"></TextBlock>

OneWayToSource

It is just opposite of Oneway.Soure is updated when the target property changes,But the target property is never updated.

<TextBlock Text="{Binding firstname , Mode=OneWayToSource}"></TextBlock>

Default

The type of bindings depends on the target property It is either twoway or oneway.

<TextBlock Text="{Binding firstname , Mode=Default}"></TextBlock>