Change the Glyph dinamically

Question

Hello I have a little issue, I want to change my Glyph, based on the order of the Listview

Here is my little method, to control that

    [AddINotifyPropertyChangedInterface]  
public class NotebooksVM {  
    public ObservableCollection<Notebook> NotebooksCollection { get; set; }  
    public ICommand ChangeLayoutCommand { get; set; }  
    public ICommand CreateNewNotebook { get; set; }  
    public ICommand SelectedNoteBookCommand { get; set; }  
    public Notebook SelectedNotebook { get; set; }  
    public LayoutBase LayoutBase { get; set; }  

    public NotebooksVM() {  

        LayoutBase = new LinearLayout();  

        NotebooksCollection = new ObservableCollection<Notebook>();  

        CreateNewNotebook = new Command(async () => {  
            var result = await Application.Current.MainPage.DisplayPromptAsync(string.Empty,  
                "Notebook name?");  

            if (!string.IsNullOrEmpty(result)) {  
                var notebook = new Notebook() {  
                    Name = result,  
                    UserId = App.UserId,  
                    CreatedAt = DateTime.Now.ToString("ddd, MMMM yyyy")  
                };  
                await Database.InsertAsync(notebook);  
                GetNotebooksAsync();  
            } else {  
                return;  
            }  
        });  
        GetNotebooksAsync();  
        SelectedNoteBookCommand = new Command(async () => {  
            await Application.Current.MainPage.Navigation.PushAsync(new NotesPage());  
            MessagingCenter.Send(this, "data", SelectedNotebook);  
            SelectedNotebook = null;  
  
        });  
        ChangeLayoutCommand = new Command(OnChangeLayout);  
          
    }  
    private async void GetNotebooksAsync() {  
        var notebooks = await Database.ReadAsync<Notebook>();  
        if (notebooks != null) {  
            notebooks.Where(notebook => notebook.Id == App.UserId);  
            NotebooksCollection.Clear();  
            foreach (var item in notebooks) {  
                NotebooksCollection.Add(item);  
            }  

        }  
    }  

    private void OnChangeLayout(object obj) {  
        if (LayoutBase is LinearLayout) {  
            LayoutBase = new GridLayout();  
        } else {  
            LayoutBase = new LinearLayout();  
        }  
    }  
}  

}

Answer 1

Hello,​

Welcome to our Microsoft Q&A platform!

To set binding for a property, it requires to specify the source. Please set BindingContext for the page, it should be the page class itemself in above code.

   public NotebooksVM()   
   {  
       ...  
       BindingContext = this;  
   }  

It's recommend to use a model class to create the properties for data binding. Here is the related code, you could refer to.

   public class TestModel : INotifyPropertyChanged  
   {  
       bool testValue;  
     
       public TestModel(bool testValue)  
       {  
           TestCommand = new Command(testMethod);  
           this.testValue = testValue;  
       }  
     
       public ICommand TestCommand { get; set; }  
       private void testMethod(object obj)  
       {  
           if (testValue)  
           {  
               IconSource = "one";  
           }  
           else  
           {  
               IconSource = "grid_";  
           }  
       }  
     
       private string iconSource = "grid_";  
       public string IconSource  
       {  
           get  
           {  
               return iconSource;  
           }  
           set  
           {  
               if (iconSource != value)  
               {  
                   iconSource = value;  
                   NotifyPropertyChanged();  
               }  
           }  
       }  
     
       protected virtual void NotifyPropertyChanged([CallerMemberName] string propertyName = "")  
       {  
           PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));  
       }  
     
       public event PropertyChangedEventHandler PropertyChanged;  
   }  
     
   public partial class TestPage : ContentPage  
   {  
       TestModel model;  
       public TestPage()  
       {  
           InitializeComponent();  
     
           model = new TestModel();  
           BindingContext = model;  
       }  
   }  

Best Regards,

Jarvan Zhang

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