private void CreateSourceBinding(object source)
{
// NOTE: We do not call the setter for DataContext here because we are
// setting up the sourceStep.
// If that method is updated we will need to make sure that this method
// does the right thing.
_dataContext = source;
_sourceStep = SourceStepFactory.Create(_bindingDescription.Source);
_sourceStep.TargetType = _targetBinding.TargetType;
_sourceStep.DataContext = source;
if (NeedToObserveSourceChanges)
{
_sourceBindingOnChanged = (sender, args) =>
{
//Capture the cancel token first
var cancel = _cancelSource.Token;
//GetValue can now be executed in a worker thread. Is it the responsibility of the caller to switch threads, or ours ?
//As the source is the viewmodel, i suppose it is the responsibility of the caller.
var value = _sourceStep.GetValue();
UpdateTargetFromSource(value, cancel);
};
_sourceStep.Changed += _sourceBindingOnChanged;
}
UpdateTargetOnBind();
}
private bool TryEvaluateif(ISourceStep testStep, ISourceStep ifStep, ISourceStep elseStep, out object value)
{
var result = testStep.GetValue();
if (result == BindingConstant.DoNothing)
{
value = BindingConstant.DoNothing;
return(true);
}
if (result == BindingConstant.UnsetValue)
{
value = BindingConstant.UnsetValue;
return(true);
}
if (IsTrue(result))
{
value = ReturnSubStepResult(ifStep);
return(true);
}
value = ReturnSubStepResult(elseStep);
return(true);
}
protected virtual object ReturnSubStepResult(ISourceStep subStep)
{
if (subStep == null)
{
return(BindingConstant.UnsetValue);
}
return(subStep.GetValue());
}
private void UpdateTargetOnBind()
{
if (NeedToUpdateTargetOnBind && _sourceStep != null)
{
_cancelSource.Cancel();
_cancelSource = new CancellationTokenSource();
var cancel = _cancelSource.Token;
try
{
var currentValue = _sourceStep.GetValue();
UpdateTargetFromSource(currentValue, cancel);
}
catch (Exception exception)
{
Log.Trace("Exception masked in UpdateTargetOnBind {0}", exception);
}
}
}