Maui 9 x:DataType & csla:PropertyInfo

[ajohnstone-ks]

We're now testing our mobile app after moving it from XF to Maui 9. One thing I noticed is that if I add an x:DataType to the page, it seems to break something with the PropertyInfo Xaml control. We have a label, bound to the IsValid of the property info, to show or hide an icon if the field was invalid. Adding x:DataType to the page though caused the label to always be visible; I don't think it was catching IsValid changing. Has anyone else experienced something like this? I have had other issues that arose after adding x:DataTypes too not related to Csla

[rockfordlhotka]

I've done very little MAUI. Really just enough to get the basic CSLA functionality working, otherwise I've focused on MAUI Hybrid (Blazor) scenarios.

It is possible that there's some bug in the PropertyInfo control. Can you provide an isolated repro?

[ajohnstone-ks]

I actually suspect its a problem with the compiled bindings. With no other changes, just removing x:DataType fixes it. And there are other places Csla isn't involved where x:DataType breaks the binding (to a command on the VM for example) but I've been able to find work arounds for those. I'll try to do a sample anyway, at the very least maybe we can figure out a workaround. I have a feeling this will affects others eventually too.

[ajohnstone-ks]

@rockfordlhotka Ok, I was able to create a repo for this issue here. Would apprecitate any help!

https://github.com/ajohnstone-ks/PropertyInfoDataType

[ajohnstone-ks]

So as another update to this, I found that if you replace

x:DataType="vm:InvoiceViewModel"

with

x:DataType="{x:Type vm:InvoiceViewModel}"

This go back to working normally. Very weird.

[rockfordlhotka]

@Bowman74 would you have time or interest in trying to sort out this issue?

[Bowman74]

Yeah, I'll take a look. Something about this is tickling my memory and I don't believe it is a CSLA thing but a MAUI thing. I may even had a bug in for it.

[Bowman74]

@ajohnstone-ks
Hard to say without seeing all the xaml. However, I suspect this has to do with the compiled bindings and their requirements introduced in .Net 9. Do you have MauiEnableXamlCBindingWithSourceCompilation set?

It feels similar to this issue:

dotnet/maui#26467

Just some more information on how to properly use compiled bindings:

"To use compiled bindings in XAML, the x:DataType attribute must be set to a string literal, or a type using the x:Type markup extension."

https://github.com/dotnet/docs-maui/blob/main/docs/fundamentals/data-binding/compiled-bindings.md

[ajohnstone-ks]

@Bowman74 Yes, I'm positive its related to the compiled bindings, as it didn't happen until we turned them on and started use x:datatype. I did mention that I didn't think this was actually a Csla thing in my last comment, when I found that x:DataType="{x:Type ns:Class}" makes the property info work correctly again.

[Bowman74]

@ajohnstone-ks
Sounds good. Sounds like the answer is it is expected behavior with .Net 9 MAUI compiled bindings. I'll close this one up.

So as another update to this, I found that if you replace
x:DataType="vm:InvoiceViewModel"
with
x:DataType="{x:Type vm:InvoiceViewModel}"
This go back to working normally.

@rockfordlhotka