utu:AncestorBinding or ItemControlBinding from Data template to parented Grid.ColumnDefinition.Width

[DevTKSS]

What would you like to be added:

Sample for how to access the ColumnEidth of the Patented Grid.ColumnDefinitions.ColumnDefinition[0]. ActualContentWidth (or similar just to get the available width (recognizing defined padding!) from there.
My attempt is following one, but struggling on the effective type which could be ColumnDefinition but no selection of which I want? 🤔 maybe the collection? And which property would be the fitting one?

<Page.Resources>
   <DataTemplate [...]>
      <StackPanel Width="{utu:AncestorBinding AncestorType=

Grid, ColumnDefinition or ColumnCollection might be possible...

Why is this needed:

Had multiple applications where this would be nice to have known the solution for this

For which Platform:

• WebAssembly
• Android
• iOS
• macOS (AppKit)
• Mac Catalyst
• Skia
  • WPF
  • GTK (Linux)
  • Linux Framebuffer
  • Tizen
• Windows

Anything else we need to know?

I would be willing if anyone can help me solve this knowledge void, to add it to the docs for future people searching for it

[Xiaoy312]

There are several problems in this approach:

1. AncestorBinding only resolve the value once, during its FrameworkElement.Loaded. This could read the wrong initial/unstabilized size, and miss the updated sizes from the user rotating/re-sizing the app, or content layout change.
2. the indexer part of ColumnDefinitions[i].Width doesnt even seem to be resolvable with binding path
   
3. Grid is a panel that is frequently used within control-template of many controls, like: GridView, FeedView, TabBar... So you may not even able to reach the desired Grid with AncestorBinding, since it may stops on a Grid before the one you want.

What I would suggest is to create a custom behavior, that seeks the proper Grid and hook into a relevant event to listen for column size change and update your controls. note: There is none. You would likely have to plant some hidden control to detect the column change by proxy, by hooking into their SizeChanged.

[DevTKSS]

Hm... Would there be a better way to do this without this already very complicated sounding event binding? Anything else than hardcoded? Maybe Regular Binding to Parent or DataContext?

[Xiaoy312]

The problem you are trying to solve itself is somewhat complicated and specific one. Complex in the sense that it cannot be answered by pure xaml without hardcoding. One major problem here is the fact that ColumnDefinition.ActualWidth is not even a dependency property, meaning that you cannot continuously receive update to this value via binding. While you could receive the updates for Width however, but this would be a value that you hardcoded in the xaml, rendering it useless for your desired usage.

Regular binding would be possible here, if you bind back the column's ActualWidth to your view-model, and then bind the target control width to that value.

Also, it sounds like you have a XY problem here. Are you trying to match width across two ListViews, or "columns" that doesn't share the same parent Grid? If that was the case, it would easier to state your ultimate goal directly.

[DevTKSS]

My problem(s) I did need this or in exchange the Height to bind to, are specifically:

I did dry to define a HeaderTemplate-DataTemplate for e.g. a ListView but same time a GridView, thats nested in a FeedView, and so I need to bind for example to the FeedViewState. So I set the DataType already to this Property and have no chance to also get a second DataType of course.

This Header has a Grid with:

1. PersonPicture or a Image depends on the shape I want in the end. But lets say its a Image. This needs to get set a specific width or Height to not look very awkward because it will be original size instead of just taking the space it got.
2. TextBlock which has to get fed a locaized String
3. A AppBarButton (just for the native Icon Property) that is binding to the Command Refresh.

Tryed in this right here to also seperate this into a CustomControl to implement a callback, but that did fail on HotReload this time, with the log, it did not find this Control it initially loaded successfully, but as I tryed to edit this wile HotReload that failed.

So to have the Width not fixed in the DataTemplate, I wanted to bind to that Heigh/Width of the Grid above, but since that Grid might not be the direct Parent, thats a problem to me. For example, when I name a ParentType to be Grid, but needing the width of a specific Column or Row from it, I only came to the Column-/RowDefinitions Property but I have no Idea how to access a specific one of those. Maybe thats kind of easy for a expert, but thats why I am asking...

[DevTKSS]

would it maybe be possible to get a DataTemplate thing that accepts a Array of DataTypes? Just to get the Properties of a FeedViewState + Other type available in a DataTemplete? I did see on some thing a Extension of .VisualTree but no Idea how to use this in a application. Maybe that can do something in this case, maybe not...