Linq Xaml Linq to Xml

Extracting TheCollection from XAML Objects Using LINQ to XML

When dealing with XAML object graphs, developers often face challenges extracting specific data, especially when the object structure and names can vary at runtime. One common scenario is needing to access a public collection within a serialized object, such as TheCollection, without knowing the exact type of the parent object at compile time.

In this blog post, we’ll explore how to use LINQ to XML to traverse a XAML object graph and extract the desired collection, even when the structure is dynamic.

Understanding the Problem

Let’s say you have a XAML serialized object that looks something like this:

<MyObject xmlns.... >
    <MyObject.TheCollection>
        <PolymorphicObjectOne .../>
        <HiImPolymorphic ... />
    </MyObject.TheCollection>
</MyObject>

In this example, your goal is to extract the TheCollection elements, which might contain various types that implement a certain interface, IPolymorphicLol. However, you may not know the name of MyObject or the details of its structure at runtime, adding a layer of complexity to the task.

Solution Overview

To effectively extract the desired collections, follow these steps:

  1. Traverse the XML structure to find elements whose names end with .TheCollection.
  2. Return the parent elements of those collections dynamically.
  3. Utilize Mono.Cecil for type analysis to determine if the found elements implement the desired interface when needed.

Step 1: Traversing the XML Structure

Using LINQ to XML, we can create a method that searches through the elements of the XAML object graph:

static IEnumerable<XElement> FindElement(XElement root)
{
    foreach (var element in root.Elements())
    {
        if (element.Name.LocalName.EndsWith(".TheCollection"))
        {
            yield return element.Parent; // Return the parent element
        }
        
        // Recursive call to search through child elements
        foreach (var subElement in FindElement(element))
        {
            yield return subElement;
        }
    }
}

Step 2: Recursive Element Lookup

The FindElement method uses recursion to traverse the XML tree. It checks each element, and if it encounters a child with a name ending in .TheCollection, it yields the parent element. This allows you to navigate through potentially deep hierarchies to locate all relevant collections.

Step 3: Implementing Type Checking

To ensure that the elements you found in your LINQ query conform to a certain interface, you will need to analyze your assemblies. The Mono.Cecil library is recommended for this purpose as it allows you to inspect the metadata of your assemblies without using reflection.

  • Why Mono.Cecil?
    It is a powerful framework that makes it easier to work with .NET assemblies, especially useful for analyzing types and interfaces without the overhead of reflection.

Conclusion

By utilizing LINQ to XML to traverse a dynamic XAML structure and combining it with powerful libraries like Mono.Cecil for type analysis, you can extract and work with specific parts of complex object graphs more efficiently. This approach provides a flexible solution adaptable to various runtime scenarios you may encounter in your applications.

Feel free to adapt the provided code to fit the specific needs of your project and enhance your capabilities of managing XAML object graphs in .NET.