Calling one of child pages of TabbedPage to reach entry text

Question

I know, "It is highly recommended to use MVVM" but I am just trying to understand and learn xamarin.forms structure. So here is the question: My application is based on TabbedPage which consists of two NavigationPage:

<TabbedPage.Children >
    <NavigationPage Title="Search">
        <NavigationPage.Icon>
            <OnPlatform x:TypeArguments="FileImageSource">
                <On Platform="iOS" Value="tab_feed.png"/>
            </OnPlatform>
        </NavigationPage.Icon>
        <x:Arguments>
            <views:SearchPage />                
        </x:Arguments>
    </NavigationPage>

    <NavigationPage Title="Study">
        <NavigationPage.Icon>
            <OnPlatform x:TypeArguments="FileImageSource">
                <On Platform="iOS" Value="tab_about.png"/>
            </OnPlatform>
        </NavigationPage.Icon>
        <x:Arguments> <!---->
            <views:AboutPage />
        </x:Arguments>
    </NavigationPage>
</TabbedPage.Children>

I am trying to call a child of this tabbedpage from a method created in a different class/view model to reach SearchBar text:

    public async void AddToList()
    {
        var mp = (MainPage)App.Current.MainPage;
        var sp = (SearchPage)mp.Children[0]; /// exception related with casting is thrown.
        var Word = sp.WordSearchBar.Text;
        ...
    }

SearchPage is defined as below. So I what is the issue creating casting exception. And how I can reach the searcbar text (other than bindings and MVVM)

public partial class SearchPage : ContentPage
{....}

Answer 1

mp.Children[0]; is kind of NavigationPage not SearchPage, so you get the casting exception.

One way to achieve that is create a static property in the App class:

public partial class `App` : Application
{
    public static AboutPage aboutPageInstance { get; set; }

    public App()
    {
        InitializeComponent();

        DependencyService.Register<MockDataStore>();
        MainPage = new MainPage();
    }
}

Then assign the value in the AboutPage and let's say you have a label called currentLabel in the AboutPage:

public partial class AboutPage : ContentPage
{
    public Label currentLabel { get; set; }

    public AboutPage()
    {
        InitializeComponent();

        currentLabel = myLabel;
        App.aboutPageInstance = this;
    }
}

Then you can access the label in other ContentPage by:

async void AddToList(object sender, EventArgs e)
{

    if (App.aboutPageInstance != null)
    {
        AboutPage about = App.aboutPageInstance;

        about.currentLabel.Text = "kkk";
    }
}

MessagingCenter is also a good option to communicate between two different ContentPages.