protected object ParseValue(string str)
{
if (str.StartsWith("{}")) // {} = escape sequence
{
return(str.Substring(2));
}
if (!str.StartsWith("{"))
{
// Normal value, no markup extension
return(str);
}
// Object/markup extension instantiation in attribute value syntax
if (!str.EndsWith("}"))
{
throw new XamlParserException("Object instantiation expression '{0}' must be terminated by a '}}' character", str);
}
string expr = str.Substring(1, str.Length - 2).Trim(); // Extract the expression
ElementContextInfo elementContext = _elementContextStack.PushElementContext(expr);
try
{
// Step 1: Process namespace declarations (doesn't apply here)
string extensionName;
IList <KeyValuePair <string, string> > parameters;
bool namedParams;
AttributeValueInstantiationParser.ParseInstantiationExpression(
expr, out extensionName, out parameters, out namedParams);
string namespaceURI;
LookupNamespace(extensionName, out extensionName, out namespaceURI);
IInitializable initializable = null;
if (namedParams)
{
// Parameters given in a Name=Value syntax
// Step 2: Instantiate the element
elementContext.Instance = GetNamespaceHandler(namespaceURI).InstantiateElement(
this, extensionName, new List <object>()); // Invoke default constructor
initializable = elementContext.Instance as IInitializable;
if (initializable != null)
{
initializable.StartInitialization(this);
}
// Step 4: Members and events in attribute syntax
// We only process the given parameters and assign their values to the
// target members. Property value inheritance, for example the
// inheritance of a "Context" member for bindings, has to be
// implemented on the visual's element class hierarchy.
foreach (KeyValuePair <string, string> parameter in parameters) // Assign value to each specified member
{
string memberName = parameter.Key;
IDataDescriptor dd;
if (ReflectionHelper.FindMemberDescriptor(elementContext.Instance, memberName, out dd))
{
object paramVal = ParseValue(parameter.Value);
HandleMemberAssignment(dd, paramVal);
// Step 4: Name registration
if (memberName == "Name")
{
string value = Convert(paramVal, typeof(string)) as string;
RegisterName(value, elementContext.Instance);
}
}
else
{
throw new XamlBindingException(
"XAML parser: Member '{0}' was not found on element type '{1}'",
memberName, elementContext.Instance.GetType().Name);
}
}
}
else
{
// Parameters given as constructor parameters
// Step 2: Instantiate the element
IList <object> flatParams = new List <object>();
foreach (string param in AttributeValueInstantiationParser.ExtractParameterValues(parameters))
{
object value = ParseValue(param);
IEvaluableMarkupExtension evaluableMarkupExtension = value as IEvaluableMarkupExtension;
if (evaluableMarkupExtension != null)
{
evaluableMarkupExtension.Initialize(this);
if (!evaluableMarkupExtension.Evaluate(out value))
{
throw new XamlParserException("Could not evaluate markup extension '{0}'", evaluableMarkupExtension);
}
}
flatParams.Add(value);
}
elementContext.Instance = GetNamespaceHandler(namespaceURI).InstantiateElement(this, extensionName, flatParams);
initializable = elementContext.Instance as IInitializable;
if (initializable != null)
{
initializable.StartInitialization(this);
}
// Step 4: Members and events in attribute syntax (doesn't apply here)
}
// Step 5: Member values in member element syntax (doesn't apply here)
// Step 6: Handle child elements (doesn't apply here)
// Step 7: Initialize
if (initializable != null)
{
initializable.FinishInitialization(this);
}
return(elementContext.Instance);
}
finally
{
_elementContextStack.PopElementContext();
}
}
/// <summary>
/// Instantiates the specified XML element located under the current element context
/// in the <see cref="_elementContextStack"/> and sets the resulting element up.
/// </summary>
/// <remarks>
/// Before calling this, the parent element, which is the current top element
/// on the element context stack, has to be instantiated and its namespaces
/// have to be imported. In the current implementation, its attributes will
/// also already be processed.
/// When this method returns, the returned visual element is completely set up,
/// this means, it was instantiated, its members and events were processed
/// and its content member was assigned. The processing of the complete
/// structure under <paramref name="currentElement"/> has finished.
/// </remarks>
/// <param name="currentElement">The XML element under the
/// current element on the element's context stack, which has to be
/// instantiated and set up.</param>
/// <param name="key">Will be set if an <c>x:Key</c> attribute was set on the
/// element to parse.</param>
/// <returns>Instantiated XAML visual element corresponding to the
/// specified <paramref name="currentElement"/>.</returns>
protected object Instantiate(XmlElement currentElement, out object key)
{
ElementContextInfo elementContext = _elementContextStack.PushElementContext(currentElement);
try
{
string name = null;
key = null;
IList <XmlAttribute> remainingAttributes = new List <XmlAttribute>(currentElement.Attributes.Count);
// Step 1: Process namespace declarations (to be done first)
foreach (XmlAttribute attr in currentElement.Attributes)
{
// We have to sort out namespace declarations.
// For both declarations xmlns="..." and xmlns:xx="...", the parser returns the
// namespace URI "http://www.w3.org/2000/xmlns/" (static constant
// <see cref="XMLNS_NS_URI"/>) for the attribute, so we check for this
// namespace URI. The value of the attribute (for example
// "http://schemas.microsoft.com/winfx/2006/xaml") is the URI
// of the namespace to be imported.
if (attr.NamespaceURI == XMLNS_NS_URI)
{
string importNamespaceURI = attr.Value;
INamespaceHandler handler;
if (importNamespaceURI == XamlNamespaceHandler.XAML_NS_URI)
{
// Implicit namespace: Use default x:-handler
handler = new XamlNamespaceHandler();
}
else if (importNamespaceURI.StartsWith("clr-namespace:"))
{
handler = ImportClrNamespace(importNamespaceURI);
}
else
{
handler = _importCustomNamespace(this, importNamespaceURI);
}
_elementContextStack.RegisterNamespaceHandler(importNamespaceURI, handler);
}
else
{
// Store other attributes so we don't need to sort out the namespace declarations in step 3
remainingAttributes.Add(attr);
}
}
// Step 2: Instantiate the element
elementContext.Instance = GetNamespaceHandler(currentElement.NamespaceURI).
InstantiateElement(this, currentElement.LocalName, new List <object>());
IInitializable initializable = elementContext.Instance as IInitializable;
if (initializable != null)
{
initializable.StartInitialization(this);
}
// Step 3: Name registration and check for x:Key (to be done before child objects are built)
foreach (XmlAttribute attr in remainingAttributes)
{
CheckNameOrKey(attr, ref name, ref key);
}
foreach (XmlNode node in currentElement.ChildNodes)
{
CheckNameOrKey(node, ref name, ref key);
}
if (name != null)
{
RegisterName(name, elementContext.Instance);
}
// Step 4: Members and events in attribute syntax
foreach (XmlAttribute attr in remainingAttributes)
{
HandleMemberOrEventAssignment(attr);
}
// Step 5: Member values in member element syntax
foreach (XmlNode node in currentElement.ChildNodes)
{
// Hint: We do not enforce, that object elements, which are used to fill the
// XAML content member within an object element, must be contiguous
if (node is XmlElement && node.LocalName.IndexOf('.') != -1) // "." is used as indicator that we have a member declaration
{
// Check XML attributes on member element - only x:Uid is permitted
foreach (XmlAttribute attr in node.Attributes)
{
if (attr.NamespaceURI != XamlNamespaceHandler.XAML_NS_URI || attr.LocalName != "Uid")
{
throw new XamlParserException("No attributes are allowed on member elements except x:Uid");
}
// TODO: Handle x:Uid markup extension
}
HandleMemberOrEventAssignment(node);
}
}
// Step 6: Handle child elements
if (elementContext.Instance is INativeXamlObject)
{ // Implementors of INativeXamlObject will handle their XAML child elements theirselves
((INativeXamlObject)elementContext.Instance).HandleChildren(this, currentElement);
}
else
{ // Content member value/Children handled by this XAML parser
object value = ParseValue(currentElement);
if (value != null)
{
IDataDescriptor dd;
if (elementContext.Instance is IContentEnabled &&
((IContentEnabled)elementContext.Instance).FindContentProperty(out dd))
{
HandleMemberAssignment(dd, value);
}
else if (ReflectionHelper.CheckHandleCollectionAssignment(elementContext.Instance, value))
{
}
else
{
throw new XamlBindingException("Visual element '{0}' doesn't support adding children",
currentElement.Name);
}
}
}
// Step 7: Initialize
if (initializable != null)
{
initializable.FinishInitialization(this);
}
return(elementContext.Instance);
}
finally
{
_elementContextStack.PopElementContext();
}
}