Bind to a static variable inside App.xaml

Question

Hi,

How can I bind my XAML to a static variable inside the App.xaml.cs?

For example:

namespace Mawaqeet
{
    public partial class App : Application
    {
        public static string my_name { get; set; }
        public static DateTime my_birthday { get; set; }

        public App()
        {

and then:

<Label Text="{Binding App.my_name}" />
<Label Text="{Binding my_birthday, StringFormat='{0:MMMM dd}'}" />

Thanks,
Jassim

Answer 1

Hello,​

Welcome to our Microsoft Q&A platform!

How can I bind my XAML to a static variable inside the App.xaml.cs

For this function, try using ResourceDictionary to store the resources. Then reference and apply the resource to elements by using the StaticResource or DynamicResource markup extension.

To Label.Text is type of string, so please use a string value instead. You could create the resource for 'my_birthday' in code and use DynamicResource markup extension to apply it.

Check the code:

   //App.xaml  
   <Application xmlns="http://xamarin.com/schemas/2014/forms"  
                xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"  
                x:Class="TestApplication_5.App">  
       <Application.Resources>  
           <x:String x:Key="my_name">MyName</x:String>  
       </Application.Resources>  
   </Application>  
     
   //App.xaml.cs  
   public partial class App : Application  
   {  
       public App()  
       {  
           InitializeComponent();  
           MainPage = new NavigationPage(new TestPage());  
     
           DateTime date = xxx;  
           Application.Current.Resources.Add("my_birthday", date.ToString());  
       }  
       ...  
   }  

Consume the resources in the page.xaml.

   <StackLayout>  
       <Label Text="{StaticResource my_name}" />  
       <Label Text="{DynamicResource my_birthday}" />  
   </StackLayout>  

Related doc: https://learn.microsoft.com/en-us/xamarin/xamarin-forms/xaml/resource-dictionaries

Best Regards,

Jarvan Zhang

---

If the response is helpful, please click "Accept Answer" and upvote it.

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 2

I needed something similar, but it wasn't easy to find any good examples, so I'm posting a solution here that worked well for me. A custom markup extension can be used to return different strings:

// App.xaml

<maui:MauiWinUIApplication
    x:Class="MyNamespace.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:maui="using:Microsoft.Maui"
    xmlns:local="using:MyNamespace">
	<maui:MauiWinUIApplication.Resources>
		<DataTemplate x:Key="MauiAppTitleBarTemplate">
			<Grid Height="32" VerticalAlignment="Stretch">
				<TextBlock Margin="10,0,0,0" VerticalAlignment="Center" Text="{local:GetResourceString Key=ProductName}" FontSize="11pt" />
			</Grid>
		</DataTemplate>
	</maui:MauiWinUIApplication.Resources>
</maui:MauiWinUIApplication>

// GetResourceString.cs

using Microsoft.UI.Xaml.Markup;

namespace MyNamespace
{

	[MarkupExtensionReturnType(ReturnType = typeof(string))]
	public sealed class GetResourceString: MarkupExtension
	{
		public string Key { get; set; }

		protected override object ProvideValue()
		{
			switch (this.Key) {
				case "ProductName":
					return MyNamespace.App.ProductName;
				default:
					return "Invalid string key.";
			}
		}
	}

}