InvalidCastException when remove item in ObservableCollection - wpf

Question

I am doing a project using WPF and Prims.
When remove category in Categories, an error has occurred.
public ObservableCollection<CategoryModel> _categories;
public ObservableCollection<CategoryModel> Categories
{
get { return _categories; }
set
{
SetProperty(ref _categories, value);
}
}
public void OnNavigatedTo(NavigationContext navigationContext)
{
_journal = navigationContext.NavigationService.Journal;
var category = navigationContext.Parameters["categoryAdd"] as CategoryModel;
if (category != null)
Categories.Add(category);
category = navigationContext.Parameters["categoryDelete"] as CategoryModel;
if (category != null)
{
foreach(var elm in Categories)
if (elm.Id == category.Id)
Categories.Remove(elm); //⇒Error here
}
}
Error:
System.InvalidCastException: 'Cannot cast an object of type' System.Windows.Controls.SelectionChangedEventArgs' to type 'SaleManager.Wpf.Admin.Models.CategoryModel'. '
Why does this error occur? How to fix it?

Answer 1

You can't change a collection in a foreach while reading this collection.
you can do this:
var item = Categories.FirstOrDefault(elm=> elm.Id == category.Id);
Categories.Remove(item);

Answer 2

Use a for loop and iterate backwards. elm is supposed to be a CategoryModel:
if (category != null)
{
for (int i = Categories.Count - 1; i >= 0; --i)
{
CategoryModel elm = Categories[i];
if (elm.Id == category.Id)
{
Categories.Remove(elm);
}
}
}