How does “UpdateSourceTrigger” affect bindings?( C# WPF interview questions with answers)

With this question sometimes interviewers ask about WPF bindings basics you can read about the same from

“UpdateSourceTrigger” decides when the data should get updated between WPF objects that are binded. In other word should data get updated in lost focus, in data change event etc.

There are four modes by which “UpdateSourceTrigger” can be defined:-

  • Default: – If it’s a text property then data is changed during lost focus and for normal property its property changed.
  • PropertyChanged: – In this setting data is updated as soon as the value is changed.
  • LostFocus: – In this setting data is updated as soon as lost focus event occurs.
  • Explicit: – In this setting the data is updated manually. In other words to update data between two WPF object’s you need to call the below code so that data is updated.

BindingExpression binding =txt1.GetBindingExpression(TextBox.TextProperty);

To set “UpdateSourceTrigger” we need to use the bindings properties as shown in the below figure.


Below video explain what is WPF and how they differ from Windows form


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