How can I create a binding in code-behind that doesn't specify a Path?

Question

I was answering another question about creating a binding in code-behind, and my original attempt at answering it was to post binding code that didn't specify a Path. This binding compiles fine, however the value is never updated. If I change the binding to use a Path, it works fine.

Why is this? And what is the correct way to create a binding in code-behind that doesn't have a Path? For example, how would I recreate Value="{Binding }" in code-behind?

Non-Working code:

Binding b = new Binding();
b.Source = SomeInt;
b.Mode = BindingMode.OneWay;
MyProgressBar.SetBinding(ProgressBar.ValueProperty, b);

SomeInt = 50;

Working code:

Binding b = new Binding();
b.Source = this;
b.Path = new PropertyPath("SomeInt");
MyProgressBar.SetBinding(ProgressBar.ValueProperty, b);

SomeInt = 50;

Answer 1

The binding engine subscribes to INPC and DP-changes on the Source object (and non-leaves on the Path), and checks whether the Path property/properties was/were changed. If there is no Path there are no notifications. A rather unfortunate drawback.

(I might be oversimplifying the system a bit but the essence is that there are no updates to source-changes, they are not and cannot be monitored)

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{Binding} is equivalent to new Binding() (no additional properties), this binding may update as there are events for DataContext changes.