AttributeData.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / cdf / src / NetFx40 / Tools / System.Activities.Presentation / System / Activities / Presentation / Base / Core / Internal / Metadata / AttributeData.cs / 1305376 / AttributeData.cs
                        

                        
                            //---------------------------------------------------------------- 
// Copyright (c) Microsoft Corporation.  All rights reserved.
//---------------------------------------------------------------
namespace System.Activities.Presentation.Internal.Metadata
{ 
    using System;
    using System.Collections.Generic; 
    using System.Text; 
    using System.Diagnostics;
    using System.Runtime; 

    // This class groups Attribute with its AttributeUsageAttributes that we care about.
    // Basically, each Attribute has characteristics that are useful to know about,
    // such as whether it can be inherited and whether there can be more than 
    // one instance of that attribute extending whatever it is the attribute
    // is extending (class, method, property, or event).  Those characteristics 
    // are stored as attributes themselves and, as such, are costly to retrieve. 
    // This class retrieves that information exactly once, on demand, and caches it for
    // further use. 
    internal class AttributeData
    {

        private Type _attributeType; 
        private bool? _isInheritable;
        private bool? _allowsMultiple; 
 
        // 
        // Creates an AttributeData wrapper around Attribute type to expose its 
        // Inherit and AllowMultiple characteristics
        // 
        // Attribute type to wrap around
        internal AttributeData(Type attributeType) 
        {
            Fx.Assert(attributeType != null, "attributeType parameter should not be null"); 
            _attributeType = attributeType; 
        }
 
        // 
        // Gets the contained attribute type
        // 
        internal Type AttributeType 
        {
            get { 
                return _attributeType; 
            }
        } 

        // 
        // Gets the AllowMultiple characteristic of the
        // contained attribute and caches the result for subsequent 
        // calls to this property.
        //  
        internal bool AllowsMultiple 
        {
            get { 
                if (_allowsMultiple == null)
                {
                    ParseUsageAttributes();
                } 

                return (bool)_allowsMultiple; 
            } 
        }
 
        // 
        // Gets the Inherit characteristic of the
        // contained attribute and caches the result for subsequent
        // calls to this property. 
        // 
        internal bool IsInheritable 
        { 
            get {
                if (_isInheritable == null) 
                {
                    ParseUsageAttributes();
                }
 
                return (bool)_isInheritable;
            } 
        } 

        private void ParseUsageAttributes() 
        {
            _isInheritable = false;
            _allowsMultiple = false;
            object[] usageAttributes = _attributeType.GetCustomAttributes(typeof(AttributeUsageAttribute), true); 

            if (usageAttributes != null && usageAttributes.Length > 0) 
            { 
                for (int i = 0; i < usageAttributes.Length; i++)
                { 
                    Fx.Assert(usageAttributes[i] is AttributeUsageAttribute, "usageAttributes should be of type AttributeUsageAttribute");
                    AttributeUsageAttribute usageAttribute = (AttributeUsageAttribute)usageAttributes[i];
                    _isInheritable = usageAttribute.Inherited;
                    _allowsMultiple = usageAttribute.AllowMultiple; 
                }
            } 
        } 
    }
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.

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