AttachInfo.cs source code in C# .NET

                        Code:
                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Base / MS / Internal / ComponentModel / AttachInfo.cs / 1 / AttachInfo.cs
                        
                        
                             
namespace MS.Internal.ComponentModel
{
    using System;
    using System.Collections.Generic; 
    using System.Diagnostics;
    using System.Reflection; 
    using System.Windows; 

 
    /// 
    ///     This class contains information about an attached property.  It can
    ///     tell you if the property can be attached to a given object.
    /// 
    ///    This class is thread-safe.
    ///  
    internal class AttachInfo 
    {
 
        //------------------------------------------------------
        //
        //  Internal Constructors
        // 
        //-----------------------------------------------------
 
        internal AttachInfo(DependencyProperty dp) 
        {
            _dp = dp; 
        }


        //----------------------------------------------------- 
        //
        //  Private Properties 
        // 
        //-----------------------------------------------------
 

        //
        // Returns the static Get method associated with this attached
        // property.  This can return null if the attached property 
        // has no static get method.
        // 
        private MethodInfo AttachMethod 
        {
            get 
            {
                if (!_getMethodChecked)
                {
                    _getMethod = DependencyObjectPropertyDescriptor.GetAttachedPropertyMethod(_dp); 
                    _getMethodChecked = true;
                } 
 
                return _getMethod;
            } 
        }

        //
        // Returns an array of attributes of type AttachedPropertyBrowsableAttribute. 
        //
        private AttachedPropertyBrowsableAttribute[] Attributes 
        { 
            get
            { 
                if (!_attributesChecked)
                {
                    MethodInfo m = AttachMethod;
                    object[] attributes = null; 

                    if (m != null) 
                    { 
                        AttachedPropertyBrowsableAttribute[] browsableAttributes = null;
 
                        // No need to inherit attributes here because the method is static
                        attributes = m.GetCustomAttributes(typeof(AttachedPropertyBrowsableAttribute), false);

                        // Walk attributes and see if there is a AttachedPropertyBrowsableForTypeAttribute 
                        // present.  If there isn't, fabricate one, but only if there is
                        // at least one AttachedPropertyBrowsableAttribute.  We require at 
                        // least one attribute to consider an attached property. 
                        bool seenTypeAttribute = false;
                        for (int idx = 0; idx < attributes.Length; idx++) 
                        {
                            if (attributes[idx] is AttachedPropertyBrowsableForTypeAttribute)
                            {
                                seenTypeAttribute = true; 
                                break;
                            } 
                        } 

                        if (!seenTypeAttribute && attributes.Length > 0) 
                        {
                            browsableAttributes = new AttachedPropertyBrowsableAttribute[attributes.Length + 1];
                            for(int idx = 0; idx < attributes.Length; idx++)
                            { 
                                browsableAttributes[idx] = (AttachedPropertyBrowsableAttribute)attributes[idx];
                            } 
                            browsableAttributes[attributes.Length] = ParameterTypeAttribute; 
                        }
                        else 
                        {
                            browsableAttributes = new AttachedPropertyBrowsableAttribute[attributes.Length];
                            for(int idx = 0; idx < attributes.Length; idx++)
                            { 
                                browsableAttributes[idx] = (AttachedPropertyBrowsableAttribute)attributes[idx];
                            } 
                        } 

                        // Update the _attributes last, this is how we maintain thread-safety.  There's a slight chance 
                        // that this routine will run simultaneously on two threads, but they will produce the same result
                        // anyway.

                        _attributes = browsableAttributes; 
                    }
 
                    _attributesChecked = true; 
                }
 
                return _attributes;
            }
        }
 
        //
        // Returns a custom attached property browsable attribute that 
        // verifies the parameter type is compatible.  This may return null 
        // if we've done the work and verified that there is no need for
        // such an attribute. 
        //
        private AttachedPropertyBrowsableAttribute ParameterTypeAttribute
        {
            get 
            {
                if (!_paramTypeAttributeChecked) 
                { 
                    MethodInfo m = AttachMethod;
 
                    if (m != null)
                    {
                        ParameterInfo[] parameters = m.GetParameters();
                        // The AttachMethod property should have already done the correct 
                        // work to ensure this method has the right signature.  Assert here
                        // that we assume this is the case. 
                        Debug.Assert(parameters != null && parameters.Length == 1, "GetAttachedPropertyMethod should return a method with one parameter."); 
                        _paramTypeAttribute = new AttachedPropertyBrowsableForTypeAttribute(parameters[0].ParameterType);
                    } 

                    _paramTypeAttributeChecked = true;
                }
 
                return _paramTypeAttribute;
            } 
        } 

        //------------------------------------------------------ 
        //
        //  Internal Methods
        //
        //----------------------------------------------------- 

        // 
        // Returns true if the DP can logically be attached to the 
        // given instance.  This will return false if the property
        // is not an attached property or if the property's 
        // AttachedPropertyBrowsableAttributes are not compatible with
        // this instance.
        //
        internal bool CanAttach(DependencyObject instance) 
        {
            Debug.Assert(instance != null, "Caller should validate non-null instance before calling CanAttach."); 
 
            if (AttachMethod != null)
            { 
                int numAttrs = 0;

                AttachedPropertyBrowsableAttribute[] attrs = Attributes;
                if (attrs != null) 
                {
                    numAttrs = attrs.Length; 
                    for(int idx = 0; idx < numAttrs; idx++) 
                    {
                        AttachedPropertyBrowsableAttribute attr = attrs[idx]; 

                        if (!attr.IsBrowsable(instance, _dp))
                        {
 
                            // The attribute isn't browsable.  If UnionResults is turned on, we must
                            // look for another matching attribute of the same type.  I don't expect 
                            // a very large list of attributes here, so I'd rather go n^2 than 
                            // create a list of UnionResults attributes somewhere I need to reconcile.
 
                            bool isBrowsable = false;

                            if (attr.UnionResults)
                            { 
                                Type attrType = attr.GetType();
 
                                for(int idx2 = 0; idx2 < numAttrs; idx2++) 
                                {
                                    AttachedPropertyBrowsableAttribute subAttr = attrs[idx2]; 

                                    if (attrType == subAttr.GetType() && subAttr.IsBrowsable(instance, _dp))
                                    {
                                        isBrowsable = true; 
                                        break;
                                    } 
                                } 
                            }
 
                            if (!isBrowsable)
                            {
                                return false;
                            } 
                        }
                    } 
                } 

                // We got through all matches, this property can be attached 
                // to the given instance provided we found at least one
                // attribute. If we didn't, that means the property should
                // be treated as non-visible.
 
                return numAttrs > 0;
            } 
 
            // No AttachMethod means this property is not an attached
            // property, so it cannot be attached elsewhere. 

            return false;
        }
 
        //------------------------------------------------------
        // 
        //  Private Fields 
        //
        //------------------------------------------------------ 


        private readonly DependencyProperty _dp;
        private MethodInfo _getMethod; 
        private AttachedPropertyBrowsableAttribute[] _attributes;
        private AttachedPropertyBrowsableAttribute _paramTypeAttribute; 
 
        private bool _attributesChecked;
        private bool _getMethodChecked; 
        private bool _paramTypeAttributeChecked;
    }
}
 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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