MultiValidationBehavior overwrites external BindingContext bindings

[bakerhillpins]

Description

MultiValidationBehavior doesn't respect bindings made on the BindingContext of children, it overwrites them. BaseBehavior<T> only applies a binding if one doesn't exist, while MultiValidationBehavior overwrites any existing binding.

Steps to Reproduce

This works:

 <Entry.Behaviors>
        <behaviors:TextValidationBehavior BindingContext="{Binding BindingContext.Range, Mode=OneWay, Source={x:Reference Entry}}"
                                          MaximumLength="{Binding Maximum, Mode=OneTime}"
                                          MinimumLength="{Binding Minimum, Mode=OneTime}"
                                          InvalidStyle="{StaticResource InvalidEntryStyle}" />
</Entry.Behaviors>

This doesn't:

  <Entry.Behaviors>
      <behaviors:MultiValidationBehavior>
          <behaviors:TextValidationBehavior BindingContext="{Binding BindingContext.Range, Mode=OneWay, Source={x:Reference Entry}}"
                                            MaximumLength="{Binding Maximum, Mode=OneTime}"
                                            MinimumLength="{Binding Minimum, Mode=OneTime}"
                                            InvalidStyle="{StaticResource InvalidEntryStyle}" />
      </behaviors:MultiValidationBehavior>
  </Entry.Behaviors>

Expected Behavior

The binding would be respected even though it's part of a Validation Collection.

Actual Behavior

The Binding to the ViewModel's Range property doesn't occur.

Basic Information

• Version with issue: 1.1.0
• Last known good version: None

All platforms.

Workaround

A workaround is to refactor the ViewModel so that all of the data needed for all of the ValidationBehaviors in the collection is bound to the MultiValidationBehavior with separate properties for each item of the collection.

Project

MultiValidationBug.zip

[AndreiMisiukevich]

Please verify fix
Thanks!