Passing an argument through multiple pages

Question

I have created an app in Xamarin portable class library (target platform UWP) where the user fills in a few TextBoxes in each page. I need to save this information in an xml file at the last page (on button click) and therefore I need to pass information through each page to the last one. How do I do that?

Here my serializable class:

namespace myProject
{
[XmlRoot("MyRootElement")]
        public class MyRootElement
        {
            [XmlAttribute("MyAttribute1")] //name of the xml element
            public string MyAttribute1     //name of a textboxt e.g.
            {
                get;
                set;
            }
            [XmlAttribute("MyAttribute2")]
            public string MyAttribute2
            {
                get;
                set;
            }
            [XmlElement("MyElement1")]
            public string MyElement1
            {
                get;
                set;
            }
}

Here is my first page:

namespace myProject
{
    public partial class FirstPage : ContentPage
    {
        public FirstPage()
        {
            InitializeComponent();
        }
        async void Continue_Clicked(object sender, EventArgs e)
        {
            MyRootElement mre = new MyRootElement
            {
                MyAttribute1 = editor1.Text,
                MyAttribute2 = editor2.Text,
                MyElement1 = editor3.Text
            };
            await Navigation.PushAsync(new SecondPage(mre));
        }
    }
}

Second Page looks like this as suggested by a helpful user here (I got it wrong I guess):

namespace myProject
{
    public partial class SecondPage : ContentPage
    {

        public MyRootElement mre { get; set; }

        public SecondPage(MyRootElement mre)
        {
            this.mre = mre;
            InitializeComponent();
        }

        async void Continue2_Clicked(object sender, EventArgs e)
        {
            MyRootElement mre = new MyRootElement
            {
                someOtherElement = editorOnNextPage.Text
            };
            await Navigation.PushAsync(new SecondPage(mre));
        }
    }
}

On the last page the file is created:

namespace myProject
{
    public partial class LastPage : ContentPage
    {
        private MyRootElement mre { get; set; }

        public LastPage(MyRootElement mre)
        {
            this.mre = mre;
            InitializeComponent();
        }

        private async void CreateandSend_Clicked(object sender, EventArgs e)
        {
            var s = await DependencyService.Get<IFileHelper>().MakeFileStream(); //stream from UWP using dependencyservice

            using (StreamWriter sw = new StreamWriter(s, Encoding.UTF8))
            {
                XmlSerializer serializer = new XmlSerializer(typeof(MyRootElement));
                serializer.Serialize(sw, mre);
            }
        }
    }
}

Please let me know if you need more content in order to answer my question.

Answer 1

You only need to create an instance of MyRootElement once, on your first page. After that, continue to use the same instance of subsequent pages.

async void Continue2_Clicked(object sender, EventArgs e)
{
  // use the same copy of mre you passed via the construt
  this.mre.someOtherElement = editorOnNextPage.Text

  await Navigation.PushAsync(new SecondPage(mre));
}