"Items collection must be empty before using ItemsSource."

📝 Title: "Solving the 'Items collection must be empty before using ItemsSource' Issue in WPF ListView"

✍️ Introduction:

Are you trying to display images in a WPF ListView with a WrapPanel style and encountering the dreaded "Items collection must be empty before using ItemsSource" exception? Don't worry, we've got you covered! In this blog post, we'll explore common issues related to this problem and provide easy-to-implement solutions.

🔍 Understanding the Problem:

When populating a WPF ListView with a LINQ-to-Entities queried collection of ADO.NET Entity Framework objects, you might encounter the "Items collection must be empty before using ItemsSource" exception. This issue arises when the ListView's Items collection is not empty when you assign a new ItemsSource.

🔧 Solution:

To solve this problem, follow these steps:

1. Set the ItemsSource property of the ListView to Nothing or an empty collection before assigning it a new source.

<ListView Name="ListViewImages" SelectionMode="Single" ItemsSource="{x:Null}">
    <local:ImageView />
</ListView>

1. Ensure that the ListView's Items collection is empty just before assigning a new source.

Private Sub Window1_Loaded(...) Handles MyBase.Loaded
    ListViewImages.ItemsSource = From g In db.Graphic _
                                 Order By g.DateAdded Ascending _
                                 Select g
End Sub

By setting the ItemsSource to Nothing or an empty collection before assigning a new source, you ensure that the ListView's Items collection is empty and avoid the exception.

🛠️ Example Explanation:

In the provided code example, the XAML snippet shows that the ListView's ItemsSource is bound to the current DataContext using {Binding}. However, if the ListBox's Items collection is not empty when assigning a new source, the exception will be thrown.

To avoid this, you need to explicitly set the ItemsSource property to Nothing or an empty collection (e.g., {x:Null} in XAML) before assigning a new source.

🎉 Call-to-Action:

Now that you have a clear understanding of how to solve the "Items collection must be empty before using ItemsSource" issue, you can apply this knowledge in your own WPF projects. If you found this blog post helpful, share it with your fellow developers and comment below about your experience with WPF ListView customization. Let's tackle these coding challenges together!

Enjoy coding! 🚀 🙌

Note for Markdown format:

<pre>``` code snippets ``` </pre>