private void BindTextPropertyToTargetPropertyNameOnce() { if (_firstRun) { _firstRun = false; var binding = new Binding(TargetPropertyName) { Mode = BindingMode.TwoWay, UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged, ValidatesOnDataErrors = true, NotifyOnValidationError = true }; MainTextBox.SetBinding(TextBox.TextProperty, binding); } }