WPF PropertyGrid - Add an Item to a Collection or a Dictionary

This example displays a custom collection/dictionary property in the DevExpress WPF Property Grid and allows users to add new items/entries as requirements/business needs dictate.

The following image illustrates available user actions:

To incorporate this feature in your DevExpress-powered WPF app (allow users to add new items to a collection/dictionary), set one of the following properties to true:

• PropertyGridControl.UseCollectionEditor - Toggles collection editing for the entire property grid.
• CollectionDefinition.UseCollectionEditor - Toggles collection editing for individual collections.

<dxprg:CollectionDefinition UseCollectionEditor="True" >

Implementation Details

The project includes the following examples:

• Collection - An example with a collection property.
• Dictionary - An example with a dictionary property.

The Collection Example

Use the XamlInitializer class to allow users to add an item to a collection.

1. Add the XamlInitializer class to the Window.Resources section.

   <Window.Resources>
       <dxprg:XamlInitializer Initialize="XamlInitializer_Initialize" x:Key="xamlInitializer" />
   </Window.Resources>

2. Specify a TypeDefinition and its attributes.

   <dxprg:XamlInitializer Initialize="XamlInitializer_Initialize" x:Key="xamlInitializer">
       <dxprg:TypeDefinition Type="{x:Type local:Supplier}"  Name="Supplier" Description="New Supplier"/>
   </dxprg:XamlInitializer>

3. In the XamlInitializer.Initialize event handler, initialize the new object's properties.

   private void XamlInitializer_Initialize(object sender, InstanceInitializeEventArgs e) {
       e.Instance.FirstName = "FIRSTNAME";
       e.Instance.LastName = "LASTNAME";
       e.Instance.Phone = "PHONE";
   }

The Dictionary Example

Use Property attributes to allow users to add items to a dictionary.

In this example, the DictionaryKey1Attribute class creates a unique key for a new item. Use this example as a template and create your own attribute class to generate unique keys.

1. Add a DictionaryKey1Attribute class inherited from the DevExpress.Mvvm.DataAnnotations.NewItemInstanceInitializerAttribute class.

   public class DictionaryKey1Attribute : NewItemInstanceInitializerAttribute {
       public DictionaryKey1Attribute() : base(typeof(Supplier)) { }
       public override KeyValuePair<object, object>? CreateInstance(ITypeDescriptorContext context, IEnumerable dictionary) {
           var testObject = ((DescriptorContext)context).Value as IDictionary<string, Supplier>;
           int key = testObject.Keys.Count;
           while(testObject.Keys.Contains(key.ToString()))
               key++;
           return new KeyValuePair<object, object>(key.ToString(), new Supplier());
       }
   }

2. Add the attribute to the dictionary property.

   [DictionaryKey1()]
   public IDictionary<string, Supplier> Tags { get; set; } = new Dictionary<string, Supplier>();

Documentation

• Edit the Collection
• XamlInitializer

Files to Review

Collections example:

• MainWindow.xaml (VB: MainWindow.xaml)
• MainWindow.xaml.cs (VB: MainWindow.xaml.vb)
• Products.cs (VB: Products.vb)

Dictionary example:

• MainWindow.xaml (VB: MainWindow.xaml)
• MainWindow.xaml.cs (VB: MainWindow.xaml.vb)
• Products.cs (VB: Products.vb)