Why can't I dynamically construct a System.Xml.XmlDocument?

Question

The following code fails with a 'Could not load type 'System.Xml.XmlDocument' from assembly' error:

object a = Type.GetType("System.Xml.XmlDocument", true);

I have a reference to System.Xml in which XmlDocument resides.

Any idea what I am doing wrong?

Answer 1

Use a fully qualified name, since the assembly may not yet have been loaded:

object a = Type.GetType("System.Xml.XmlDocument, System.Xml", true);

Answer 2

If you need to be able to dynamically load it from a string, this will work, you must specify the fully qualified name because there are possibly multiple versions of this dll in the GAC. Replace the Version=2.0.0.0 with the version you want to load depending on the framework version you are using.

Assembly xmlAssembly = Assembly.Load("System.Xml, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089");

Once you have loaded the assembly, you can then dynamically create an instance of the class you are after.

object xmlDoc = xmlAssembly.CreateInstance("System.Xml.XmlDocument", false);

Answer 3

You can usually get by just by appending a comma and the assembly name, i.e. "Namespace.Type, Assembly". However, if an assembly is strongly named, as System.Xml.dll is, you need to use the Type.AssemblyQualifiedName property which returns not just "Namespace.Type, Assembly" but also the signature information required to identify the assembly. This works:

var xmlDocType = Type.GetType("System.Xml.XmlDocument, System.Xml, "
    + "Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")