Create ICommand Failed

[FlytotheMuum]

Current behavior

Templates Used: https://www.nuget.org/packages/Uno.Templates 4.8.8#

ModelView

public List<Device> DeviceCollection = new() {
    new Device 
    { 
        Title="123",
        BtnCommand = new SimpleCommand(()=> { 
        //run some command
        })
    }
};
public class Device
{
    public string? Title { get; set; }
    public ICommand? BtnCommand { get; set; } 
}
/// <summary>
/// Simple naive implementation of ICommand for demo purposes
/// </summary>
internal class SimpleCommand : ICommand
{
    private readonly Action _action;

    public SimpleCommand(Action action)
    {
        _action = action;
    }

    public bool CanExecute(object? parameter)
    {
        return true;
    }

    public void Execute(object? parameter)
    {
        _action();
    }
    public event EventHandler? CanExecuteChanged;
}

/// <summary>
/// Simple naive implementation of ICommand for demo purposes
/// </summary>
internal class SimpleCommand<T> : ICommand where T : class
{
    private readonly Action<T> _action;

    public SimpleCommand(Action<T> action)
    {
        _action = action;
    }

    public bool CanExecute(object? parameter)
    {
        return parameter is T;
    }

    public void Execute(object? parameter)
    {
        if (parameter is T value)
        {
            _action(value);
        }
    }
    public event EventHandler? CanExecuteChanged;
}

Xaml

                <Grid>
                    <GridView 
                        SelectionMode="None" IsItemClickEnabled="True"
                        ItemsSource="{Binding DeviceCollection }">
                        <GridView.ItemTemplate>
                            <DataTemplate>
                                <Button 
                                Content="{Binding Title}" 
                                Command="{Binding BtnCommand }" 
                                CommandParameter="{Binding Title}" />
                            </DataTemplate>
                        </GridView.ItemTemplate>
                    </GridView>
                </Grid>

Program can't build with fail CS0067

Expected behavior

Build Sucessful

How to reproduce it (as minimally and precisely as possible)

.NET CLI

dotnet new install Uno.Templates::4.8.8
dotnet new unoapp

Workaround

......
#pragma warning disable CS0067
public event EventHandler? CanExecuteChanged;
......

Works on UWP/WinUI

None

Environment

No response

NuGet package version(s)

No response

Affected platforms

No response

IDE

Visual Studio 2022

IDE version

17.6 Preview 2.0

Relevant plugins

No response

Anything else we need to know?

No response

[jeromelaban]

Thanks for the report.

Let's discuss first here, as it seems that the behavior you're observing is appropriate, since the member really is not used. Note that the default template uses TreatWarningsAsErrors by default.

[Youssef1313]

I guess SimpleCommand isn't included in the template and it's code you wrote yourself? In that case, the behavior is correct. This warning is coming from the compiler and the template treats warnings as errors, as @jeromelaban mentioned.

Possible ways to avoid the issue (ordered in my preference):

• Use public event EventHandler? CanExecuteChanged { add { } remove { } }
• #pragma warning disable CS0067
• Write a custom DiagnosticSuppressor that disables this diagnostic interface-implemented events. This could be done in Uno itself, but since this is the less preferred option for me, I don't think we should do it. Though I definitely would defer to @jeromelaban on that in case he thinks otherwise.

[FlytotheMuum]

Hi there, Im sure This is the best way to fix this issue:
Use public event EventHandler? CanExecuteChanged { add { } remove { } }

I Get SimpleCommand from sample code:
uno-bootcamp/modules/03-Let-views-do-views/TodoApp/TodoApp.Shared/ViewModels/SimpleCommand.cs

The reason to use SimpleCommand is that I want the buttons in the Card to call the ICommand method sucessfully.

[FlytotheMuum]

<utu:Card HeaderContent="Outlined card"
          SupportingContent="{Binding DeviceCollection}"
          AutomationProperties.AutomationId="Outlined_Card_Supplemental_Action_Button">
   <utu:Card.SupportingContentTemplate>
      <DataTemplate>


               <Button 
                       Command="{Binding BtnCommand}"
                       AutomationProperties.AutomationId="Action_1_Button" 
                />


      </DataTemplate>
   </utu:Card.SupportingContentTemplate>
</utu:Card>