How to set a binding in Code

Question

I have the need to set a binding in code   I can t seem to get it right tho   This is what i have tried   XAML    lt TextBox Name  txtText  gt  lt  TextBox gt    Code behind   Binding myBinding   new Binding  SomeString    myBinding Source   ViewModel SomeString  myBinding Mode   BindingMode TwoWay  myBinding UpdateSourceTrigger   UpdateSourceTrigger PropertyChanged  BindingOperations SetBinding txtText  TextBox TextProperty  myBinding     ViewModel   public string SomeString             get                    return someString                set                     someString  value            OnPropertyChanged  SomeString                    The property is not updating when i set it    What am i doing wrong

User · Accepted Answer

Replace   myBinding Source   ViewModel SomeString    with   myBinding Source   ViewModel    Example   Binding myBinding   new Binding    myBinding Source   ViewModel  myBinding Path   new PropertyPath  SomeString    myBinding Mode   BindingMode TwoWay  myBinding UpdateSourceTrigger   UpdateSourceTrigger PropertyChanged  BindingOperations SetBinding txtText  TextBox TextProperty  myBinding     Your source should be just ViewModel  the  SomeString part is evaluated from the Path  the Path can be set by the constructor or by the Path property

User · Answer

In addition to the answer of Dyppl  I think it would be nice to place this inside the OnDataContextChanged event   private void OnDataContextChanged object sender  DependencyPropertyChangedEventArgs e           Unforunately we cannot bind from the viewmodel to the code behind so easily  the dependency property is not available in XAML   for some reason          To work around this  we create the binding once we get the viewmodel through the datacontext      var newViewModel   e NewValue as MyViewModel       var executablePathBinding   new Binding               Source   newViewModel          Path   new PropertyPath nameof newViewModel ExecutablePath               BindingOperations SetBinding LayoutRoot  ExecutablePathProperty  executablePathBinding       We have also had cases were we just saved the DataContext to a local property and used that to access viewmodel properties  The choice is of course yours  I like this approach because it is more consistent with the rest  You can also add some validation  like null checks  If you actually change your DataContext around  I think it would be nice to also call   BindingOperations ClearBinding myText  TextBlock TextProperty     to clear the binding of the old viewmodel  e oldValue in the event handler

User · Answer

You need to change source to viewmodel object   myBinding Source   viewModelObject

[c#] How to set a binding in Code?

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