AttachInfo.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Base / MS / Internal / ComponentModel / AttachInfo.cs / 1305600 / AttachInfo.cs
                        
                        
                             
namespace MS.Internal.ComponentModel
{
    using System;
    using System.Collections.Generic; 
    using System.ComponentModel;
    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(DependencyObjectPropertyDescriptor.AttachedPropertyBrowsableAttributeType, 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.");
                        TypeDescriptionProvider typeProvider = TypeDescriptor.GetProvider(_dp.OwnerType); 
                        _paramTypeAttribute = new AttachedPropertyBrowsableForTypeAttribute(typeProvider.GetRuntimeType(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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AttachInfo.cs source code in C# .NET

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