Porting WPF UpdateSourceTrigger

[pr8x]

Having something like the WPF Binding.UpdateSourceTrigger (https://docs.microsoft.com/en-us/dotnet/api/system.windows.data.binding.updatesourcetrigger?view=netframework-4.8) in Avalonia would be helpful.

[mightypanda]

The missing UpdateSourceTrigger is a headache in some scenarios:
for example:

• if you bind a numeric value to a visual property, you get unpleasant looking updates in the visual/shape while typing the number.
• If binding fires up a server-sync, the server gets many more calls that are basically useless, as well as validation errors

[maxkatz6]

If binding fires up a server-sync, the server gets many more calls that are basically useless, as well as validation errors

This part is expected to be managed on lower layer and not by View. With ReactiveUI it's quite simple using Throttle mechanism. It's always possible with some other third-parties.

if you bind a numeric value to a visual property, you get unpleasant looking updates in the visual/shape while typing the number.

Agree, in some cases for binging between elements we care only about final value after lostfocus, so UpdateSourceTrigger will be really helpful in this case.

[mightypanda]

Yes, throttling can help but it is not semantically the same, also for client->server updates it makes sense the whole data is sent as soon as the field gets a input confirmation from the user, which is often modeled as a LostFocus event.

[loonwong]

Hello,

Is this feature in your roadmap? is there a chance to see it in the next release?

[kekekeks]

For now you can use behaviors for a workaround.

        <TextBox>
            <Interaction.Behaviors>
                <example:LostFocusUpdateBindingBehavior Text="{Binding Text}"/>
            </Interaction.Behaviors>
        </TextBox>

It's a bit more verbose, but should solve your issue.

[pr8x]

Made a PR for this: #7797

[workgroupengineering]

Hi @Avaloniateam, is there any chance that the feature will be implemented? It's very annoying to add behaviors.

[MikeCodesDotNET]

There is a plan to look at the binding system but right now we're focused on shipping v11.

[heartacker]

There is a plan to look at the binding system but right now we're focused on shipping v11.

thanks and add this to milestone V11