How to create a DataTrigger programatically with Binding="{Binding}"?

Question

What's the equivelant of this DataTrigger in C# code?

<DataTrigger
  Binding="{Binding}"
  Value="{x:Null}">
    <Setter
      Property=SomeProperty
      Value=SomeValue />
</DataTrigger>

I am skeptical on how to create the Binding. Is this correct?

var trigger = new DataTrigger();
trigger.Value = null;
// Is this sufficient?
trigger.Binding = new Binding();
// Code to create the setter
// ...

You should have searched first before posting your question. social.msdn.microsoft.com/Forums/vstudio/en-US/… — Andy
– Andy, Commented Sep 9, 2021 at 17:42
I've seen this link. It's the Binding="{Binding}" that I don't know how to create. — Themelis
– Themelis, Commented Sep 9, 2021 at 17:45
trigger.Binding = new Binding("."); should be equivalent. However, neither that nor Binding="{Binding}" makes sense on a DataTrigger, because it lacks a source property that could be updated and thus trigger the Trigger. — Clemens
– Clemens, Commented Sep 9, 2021 at 18:16
A binding (created in XAML) without a Path (or a Path with value '.') will still have a the DataContext as implict Source. And the DC can change from null to not null. So in XAML it would work - on DataContextChanged event. In code behind, I think the Source must be actively, explictly set, otherwise the trigger has a no Source or null as its Source and the condition will always be true. — lidqy
– lidqy, Commented Sep 9, 2021 at 21:53
Could be when the trigger is added to a FrameworkElement's style and thus becomes part of the visual tree, the current DataContext potentially could also automatically become the Source (of the triggers Binding). Testing is above studying, as they say. — lidqy
– lidqy, Commented Sep 9, 2021 at 22:01

mm8 · Accepted Answer · 2021-09-10 14:09:37Z

1

This would be the equivalent of your XAML:

var trigger = new DataTrigger()
{
    Value = null,
    Binding = new Binding(".")
};
trigger.Setters.Add(new Setter() { Property = SomeProperty, Value = SomeValue });

answered Sep 10, 2021 at 14:09

mm8

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