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namespace MS.Internal.ComponentModel
{
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Reflection;
using System.Windows;
/// <summary>
/// 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.
/// </summary>
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;
}
}
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