Adding a new item to the combobox item source throw the following exception "'Items collection must be empty before using ItemsSource.'"

Question

I am trying to bind a list of strings to my combo box. But when I add a new item to the list or read items from the file, I receive Exception that Items collection must be empty before using ItemsSource. Remember that I need to put a button at the end of the Combobox. what can be the issue?

my Xaml code

 <ComboBox Grid.Column="1" Text="Category">
                <ComboBox.ItemsSource>
                    <CompositeCollection>
                        <CollectionContainer Collection="{Binding Categories}" />
                   <ComboBoxItem>
                    <Button Style="{StaticResource styleTextButton}"
                                    Content="New Category"
                                    Command="{Binding AddNewCategoryCommand}" 
                                    Width="235"/>
                </ComboBoxItem>
                    </CompositeCollection>
                </ComboBox.ItemsSource>
            </ComboBox>

I have read “Items collection must be empty before using ItemsSource.” but it did not help me to solve the problem.

score 0 · Answer 1 · answered Aug 10 '20 at 14:42

0

You cannot add an item directly to the Items property after you have set the ItemsSource property.

If you use an ItemsSource, you should add a new item to the source collection, i.e. Categories in this case.

Either you use an ItemsSource or you don't. It's one way or the other but not both.

answered Aug 10 '20 at 14:42

mm8

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The XAML code for what? How are you currently adding an item when you get the exception? – mm8 Aug 14 '20 at 11:00

Adding a new item to the combobox item source throw the following exception "'Items collection must be empty before using ItemsSource.'"

1 Answers1