cc @Sergio0694
Introduce a `NullableHelper` type with `GetValueOrDefaultRef` which returns a `ref T` which points to a value that is equivalent to `GetValueOrDefault`
TODO add tests
## Related to #3422
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## PR Type
What kind of change does this PR introduce?
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<!-- - Bugfix -->
<!-- - Feature -->
<!-- - Code style update (formatting) -->
- Refactoring
<!-- - Build or CI related changes -->
<!-- - Documentation content changes -->
<!-- - Sample app changes -->
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## What is the current behavior?
<!-- Please describe the current behavior that you are modifying, or link to a relevant issue. -->
Quoting from https://github.com/windows-toolkit/WindowsCommunityToolkit/issues/3422#issuecomment-774484219, we have the current situation with respect to extension methods in the Toolkit:
> On a related note - lately I've been thinking a bit about the various extensions in the toolkit in particular.
@mrlacey already pointed this out in the first post in this issue, and I agree that that inconsistency is a bit weird, especially now that newer packages have started to just place them in their respective root namespaces. Basically we have the following situation:
>
> - `Microsoft.Toolkit.Extensions` (from `Microsoft.Toolkit`)❌
> - `Microsoft.Toolkit.Extensions` (from `Microsoft.Toolkit.Diagnostics`*) ❌
> - `Microsoft.Toolkit.HighPerformance.Extensions` ❌
> - `Microsoft.Toolkit.Mvvm.Messaging` ✅
> - `Microsoft.Toolkit.Uwp.Extensions` ❌
> - `Microsoft.Toolkit.Uwp.UI.Extensions` ❌
> - `Microsoft.Toolkit.Uwp.UI.Animations` ✅
> - `Microsoft.Toolkit.Uwp.UI.Media`** ✅
## What is the new behavior?
<!-- Describe how was this issue resolved or changed? -->
This PR moves all the extensions (including XAML markup extensions) to the root namespace of each package.
It also fixes some related issues like inconsistent naming, incorrect method locations, etc.
## Open questions
Some extension types now have a number of properties that are only relevant when grouped together, as they refer a specific feature. For instance, all the SurfaceDial properties in `TextBoxExtensions`, or the ones related to Regex. @michael-hawker mentioned the "option" pattern that the Graph Controls have been using, which would look something like this:
```xml
<TextBox>
<ui:TextBoxExtentions.SurfaceDial>
<ui:SurfaceDialOptions MinValue="0" MaxValue="10" EnableHapticFeedback="True" ... />
</ui:TextBoxExtensions.SurfaceDial>
</TextBox>
```
Do we want to make this change as well while we're at it? Thoughts? 🙂
## Additional details
Haven't fully tested all the samples in the sample app just yet, have just focused on ensuring everything built fine for now.
Also, this PR is based on top of #3685, which needs to be merged before this one.
## PR Checklist
Please check if your PR fulfills the following requirements:
- [X] Tested code with current [supported SDKs](../readme.md#supported)
- [ ] ~~Pull Request has been submitted to the documentation repository [instructions](..\contributing.md#docs). Link: <!-- docs PR link -->~~
- [ ] ~~Sample in sample app has been added / updated (for bug fixes / features)~~
- [ ] ~~Icon has been created (if new sample) following the [Thumbnail Style Guide and templates](https://github.com/windows-toolkit/WindowsCommunityToolkit-design-assets)~~
- [X] New major technical changes in the toolkit have or will be added to the [Wiki](https://github.com/windows-toolkit/WindowsCommunityToolkit/wiki) e.g. build changes, source generators, testing infrastructure, sample creation changes, etc...
- [X] Tests for the changes have been added (for bug fixes / features) (if applicable)
- [X] Header has been added to all new source files (run *build/UpdateHeaders.bat*)
- [ ] Contains **NO** breaking changes
## Fixes#3763
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## PR Type
What kind of change does this PR introduce?
<!-- Please uncomment one or more that apply to this PR. -->
- Bugfix
<!-- - Feature -->
<!-- - Code style update (formatting) -->
<!-- - Refactoring (no functional changes, no api changes) -->
<!-- - Build or CI related changes -->
<!-- - Documentation content changes -->
<!-- - Sample app changes -->
<!-- - Other... Please describe: -->
## What is the current behavior?
<!-- Please describe the current behavior that you are modifying, or link to a relevant issue. -->
- Incorrect loading of display names for validated properties
- Repeated error messages after validation
## What is the new behavior?
<!-- Describe how was this issue resolved or changed? -->
Fixed the errors above.
Opening as a draft to have the CI run, but I'm still investigating the second issue from the list above.
## PR Checklist
Please check if your PR fulfills the following requirements:
- [X] Tested code with current [supported SDKs](../readme.md#supported)
- [ ] ~~Pull Request has been submitted to the documentation repository [instructions](..\contributing.md#docs). Link: <!-- docs PR link -->~~
- [ ] ~~Sample in sample app has been added / updated (for bug fixes / features)~~
- [ ] ~~Icon has been created (if new sample) following the [Thumbnail Style Guide and templates](https://github.com/windows-toolkit/WindowsCommunityToolkit-design-assets)~~
- [X] New major technical changes in the toolkit have or will be added to the [Wiki](https://github.com/windows-toolkit/WindowsCommunityToolkit/wiki) e.g. build changes, source generators, testing infrastructure, sample creation changes, etc...
- [X] Tests for the changes have been added (for bug fixes / features) (if applicable)
- [X] Header has been added to all new source files (run *build/UpdateHeaders.bat*)
- [X] Contains **NO** breaking changes
## Fixes#3707
Moves the Deferred Event Helpers to the main .NET package and leaves the Uwp specific extensions in the Microsoft.Toolkit.Uwp package.
## PR Type
What kind of change does this PR introduce?
<!-- Please uncomment one or more that apply to this PR. -->
<!-- - Bugfix -->
<!-- - Feature -->
<!-- - Code style update (formatting) -->
- Refactoring (no functional changes, no api changes)
<!-- - Build or CI related changes -->
<!-- - Documentation content changes -->
<!-- - Sample app changes -->
<!-- - Other... Please describe: -->
## What is the current behavior?
Deferred events pattern only available in UWP.
## What is the new behavior?
Deferred events pattern can be used in .NET
## PR Checklist
Please check if your PR fulfills the following requirements:
- [ ] Tested code with current [supported SDKs](../readme.md#supported)
- [ ] Pull Request has been submitted to the documentation repository [instructions](..\contributing.md#docs). Link: <!-- docs PR link -->
- [ ] Sample in sample app has been added / updated (for bug fixes / features)
- [ ] Icon has been created (if new sample) following the [Thumbnail Style Guide and templates](https://github.com/windows-toolkit/WindowsCommunityToolkit-design-assets)
- [ ] New major technical changes in the toolkit have or will be added to the [Wiki](https://github.com/windows-toolkit/WindowsCommunityToolkit/wiki) e.g. build changes, source generators, testing infrastructure, sample creation changes, etc...
- [ ] Tests for the changes have been added (for bug fixes / features) (if applicable)
- [ ] Header has been added to all new source files (run *build/UpdateHeaders.bat*)
- [ ] Contains **NO** breaking changes
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## Other information
## Contributes to #3062
Adds deprecation message to the RadialProgressBar. Updates some of our dependencies. Few more to do, but will wait until we remove parsers and services packages.
## Follow up to #3428
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This PR is for tracking all changes/fixes/improvements to the `Microsoft.Toolkit.Mvvm` package following the Preview 4.
<!-- Add a brief overview here of the feature/bug & fix. -->
## PR Type
What kind of change does this PR introduce?
<!-- Please uncomment one or more that apply to this PR. -->
- Feature
- Improvements
<!-- - Code style update (formatting) -->
<!-- - Refactoring (no functional changes, no api changes) -->
<!-- - Build or CI related changes -->
<!-- - Documentation content changes -->
<!-- - Sample app changes -->
<!-- - Other... Please describe: -->
## Overview
This PR is used to track and implement new features and tweaks for the `Microsoft.Toolkit.Mvvm` package.
See the linked issue for more info, and for a full list of changes included in this PR.
## PR Checklist
Please check if your PR fulfills the following requirements:
- [X] Tested code with current [supported SDKs](../readme.md#supported)
- [ ] ~~Pull Request has been submitted to the documentation repository [instructions](..\contributing.md#docs). Link: <!-- docs PR link -->~~
- [ ] ~~Sample in sample app has been added / updated (for bug fixes / features)~~
- [ ] ~~Icon has been created (if new sample) following the [Thumbnail Style Guide and templates](https://github.com/windows-toolkit/WindowsCommunityToolkit-design-assets)~~
- [X] Tests for the changes have been added (for bug fixes / features) (if applicable)
- [X] Header has been added to all new source files (run *build/UpdateHeaders.bat*)
- [X] Contains **NO** breaking changes
