AttributeCallback Delegate

Called when attributes are needed for a type.

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

Syntax

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

public delegate void AttributeCallback(
    AttributeCallbackBuilder builder
)

public delegate void AttributeCallback(
    AttributeCallbackBuilder^ builder
)

type AttributeCallback = 
    delegate of 
        builder:AttributeCallbackBuilder -> unit

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;

// The ProvideMetadata assembly-level attribute indicates to designers
// that this assembly contains a class that provides an attribute table. 
[assembly: ProvideMetadata(typeof(CustomControlLibrary.VisualStudio.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 IProvideAttributeTable. If found, designers instantiate 
    // this class and access its AttributeTable property automatically.
    internal class Metadata : IProvideAttributeTable
    {
        // Accessed by the designer to register any design-time metadata.
        public AttributeTable AttributeTable
        {
            get
            {
                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));
                    });

                return builder.CreateTable();
            }
        }
    }
}

See Also

Reference

Microsoft.Windows.Design.Metadata Namespace

AttributeTableBuilder

AddCallback

AttributeTable

Other Resources

Walkthrough: Creating a Design-time Adorner

Understanding WPF Designer Extensibility