passing values without heavy libraries?

Question

public partial class ScannerModalPage : ContentPage
{
    public ScannerModalPage()
    {
        InitializeComponent();
    }
    public void ZXingScannerView_OnScanResult(ZXing.Result result)
    {
        Device.BeginInvokeOnMainThread(() =>
        {
            scanResultText.Text = result.Text;
        });
    }
    private void AcceptButton_Clicked(object sender, EventArgs e)
    {
        Navigation.PopModalAsync();
    }
}

without involving MVVM, is there a simple way (mainly because this use case only needs to implement it once) to pass a value BACK to the previous page?
for some reason, i imagined this would work, but alas, it does NOT.

Navigation.PopModalAsync(result.Text());

Answer 1

Hello,

Welcome to our Microsoft Q&A platform!
You could use Action to pass value. There are two pages in my demo, when I click the button and pop the second page to the previous page(first page), I pass the label text of the second page. You can have a try with the following code:
PageOne.xaml

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"  
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"  
             x:Class="PassValueDemo.PageOne"  
             Title="PageOne">  
    <ContentPage.Content>  
        <StackLayout>  
            <Label x:Name="showResultLabel" Text="none" FontSize="Large" BackgroundColor="Pink"></Label>  
            <Button Text="Push button"  
                VerticalOptions="CenterAndExpand"   
                HorizontalOptions="CenterAndExpand"  
                    Clicked="Button_Clicked"/>  
        </StackLayout>  
    </ContentPage.Content>  
</ContentPage>  

PageOne.xaml.cs

 private void Button_Clicked(object sender, EventArgs e)  
        {  
            PageTwo second = new PageTwo();  
            second.PassValueAction = (passvalue) => {  
                Console.WriteLine("receive: {0}", passvalue);  
                showResultLabel.Text = passvalue;  
            };  
            Navigation.PushAsync(second);  
        }  

PageTwo.xaml

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"  
         xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"  
         x:Class="PassValueDemo.PageTwo"  
         Title="PageTwo">  
<ContentPage.Content>  
    <StackLayout BackgroundColor="LightBlue">  
        <Label x:Name="resultLabel" Text="result"></Label>  
        <Button Text="Pop button"  
            VerticalOptions="CenterAndExpand"   
            HorizontalOptions="CenterAndExpand"  
                Clicked="Button_Clicked"/>  
    </StackLayout>  
</ContentPage.Content>  
</ContentPage>  

PageTwo.xaml.cs

 public partial class PageTwo : ContentPage  
{  
   public Action<String> PassValueAction;//use action to pass value  
    static int tag;  
    public PageTwo()  
    {  
        InitializeComponent();  
    }  

    private void Button_Clicked(object sender, EventArgs e)  
    {  
        tag++;//test  
        PassValueAction(resultLabel.Text + tag.ToString());  
        Navigation.PopAsync();  
    }  
}  

Best Regards,
Wenyan Zhang

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