AttributeCallback Delegate

Called when attributes are needed for a type.

Namespace:  Microsoft.Windows.Design.Metadata
Assembly:  Microsoft.Windows.Design (in Microsoft.Windows.Design.dll)

Syntax

'Declaration
Public Delegate Sub AttributeCallback ( _
    builder As AttributeCallbackBuilder _
)

'Usage
Dim instance As New AttributeCallback(AddressOf HandlerMethod)

public delegate void AttributeCallback(
    AttributeCallbackBuilder builder
)

public delegate void AttributeCallback(
    AttributeCallbackBuilder^ builder
)

JScript does not support delegates.

Parameters

• builder
  Type: Microsoft.Windows.Design.Metadata.AttributeCallbackBuilder

  An AttributeCallbackBuilder that can be used to add attributes. AttributeCallbackBuilder delegates can build attributes only for the type that is requesting metadata.

Remarks

Use the AttributeCallback delegate when you are populating a large attribute table. By using the callback pattern, attribute table population is deferred until the designer needs the design-time metadata for a type.

Examples

The following code example shows how to create and populate an attribute table by using the AttributeCallbackBuilder class.

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.ComponentModel;
using System.Reflection;
using System.Windows.Media;
using System.Windows.Controls;
using System.Windows;

using Microsoft.Windows.Design.Features;
using Microsoft.Windows.Design.Metadata;

namespace CustomControlLibrary.VisualStudio.Design
{
    // Container for any general design-time metadata to initialize. 
    // Designers look for a type in the design-time assembly that  
    // implements IRegisterMetadata. If found, designers instantiate  
    // this class and call its Register() method automatically. 
    internal class Metadata : IRegisterMetadata
    {
        // Called by the designer to register any design-time metadata. 
        public void Register()
        {
            AttributeTableBuilder builder = new AttributeTableBuilder();

            // Build the attribute table by using the AttributeCallbackBuilder  
            // class. The attribute table is not populated until the designer 
            // needs it, which is more efficient for large attribute tables.
            builder.AddCallback(
                typeof(Button), 
                delegate(AttributeCallbackBuilder callbackBuilder)
            {
                callbackBuilder.AddCustomAttributes(
                    new DefaultPropertyAttribute("Content"));

                // Apply the ReadOnlyAttribute to the Background property  
                // of the Button class.
                callbackBuilder.AddCustomAttributes(
                    "Background",
                    new ReadOnlyAttribute(true));

                PropertyDescriptorCollection properties =
                    TypeDescriptor.GetProperties(typeof(Button));
                PropertyDescriptor pd = properties["Foreground"];
                callbackBuilder.AddCustomAttributes(
                    pd,
                    new ReadOnlyAttribute(true));

                callbackBuilder.AddCustomAttributes(
                   Button.WidthProperty,
                   new TypeConverterAttribute(typeof(LengthConverter)),
                   new DescriptionAttribute("This is the width"));

                MemberInfo[] members = typeof(Button).GetMember("Height");
                callbackBuilder.AddCustomAttributes(
                    members[0],
                    new ReadOnlyAttribute(true));
            });

            MetadataStore.AddAttributeTable(builder.CreateTable());
        }
    }
}

See Also

Reference

Microsoft.Windows.Design.Metadata Namespace

AttributeTableBuilder

AddCallback

AttributeTable

Other Resources

Metadata Store

Walkthrough: Creating a Design-time Adorner

Understanding WPF Designer Extensibility