XmlSerializer fails on object loaded from an activated assembly

[christopher.watford]

I'm loading a plugin assembly using Activator.CreateInstanceFrom, and
inside this assembly is a settings class which gets serialized to XML.

The general code flow is as follows:

ObjectHandle pluginHandle = Activator.CreateInstanceFrom(assemblyName,
type);
object plugin = pluginHandle.Unwrap();
....

// Settings is from the plugin Assembly loaded by the Activator
XmlSerializer x = new XmlSerializer(typeof(Settings));
x.Serialize(settingsFile, _settings);
// blows up here with this exception:

System.InvalidOperationException: There was an error generating the
XML document. ---System.InvalidCastException: Unable to cast object
of type '*.Settings' to type '*.Settings'.
at
Microsoft.Xml.Serialization.GeneratedAssembly.XmlS erializationWriterSettings.Write3_Settings(Object
o)
Which is confusing considering the types are identical. However, when
I add the following XML to App.Config, the error goes away:

<system.diagnostics>
<switches>
<add name="XmlSerialization.Compilation" value="4" />
</switches>
</system.diagnostics>

What am I missing w.r.t. Activator.CreateInstanceFrom and
XmlSerializer?

Thanks.

[christopher.watford]

On Apr 9, 10:53 am, [e-mail] wrote:

I'm loading a plugin assembly using Activator.CreateInstanceFrom, and
inside this assembly is a settings class which gets serialized to XML.

The general code flow is as follows:

ObjectHandle pluginHandle = Activator.CreateInstanceFrom(assemblyName,
type);
object plugin = pluginHandle.Unwrap();
...

// Settings is from the plugin Assembly loaded by the Activator
XmlSerializer x = new XmlSerializer(typeof(Settings));
x.Serialize(settingsFile, _settings);
// blows up here with this exception:

System.InvalidOperationException: There was an error generating the
XML document. ---System.InvalidCastException: Unable to cast object
of type '*.Settings' to type '*.Settings'.
at
Microsoft.Xml.Serialization.GeneratedAssembly.XmlS erializationWriterSettings.Write3_Settings(Object
o)

Which is confusing considering the types are identical. However, when
I add the following XML to App.Config, the error goes away:

<system.diagnostics>
<switches>
<add name="XmlSerialization.Compilation" value="4" />
</switches>
</system.diagnostics>

What am I missing w.r.t. Activator.CreateInstanceFrom and
XmlSerializer?

Thanks.

Moreover, *any* type from a loaded assembly (Assembly.Load,
Assembly.LoadFile, Assembly.LoadFrom, Activator.CreateInstanceFrom)
fails to be serialized/deserialized.

Assembly asm = Assembly.LoadFrom(Path.GetFullPath(assemblyName));
object plugin = asm.CreateInstance(type);
((IPlugin)plugin).WriteSettings(textWriter);

....

public class XmlTest { public string Hello = "Hello World!"; }

public void WriteSettings(TextWriter settingsWriter)
{
XmlSerializer x = new XmlSerializer(typeof(XmlTest));
x.Serialize(settingsWriter, new XmlTest());
}
Once again, if I use the diagnostic switches, everything works fine.

[christopher.watford]

On Apr 9, 11:26 am, [e-mail] wrote:

On Apr 9, 10:53 am, [e-mail] wrote:

I'm loading a plugin assembly using Activator.CreateInstanceFrom, and
inside this assembly is a settings class which gets serialized to XML.

The general code flow is as follows:

ObjectHandle pluginHandle = Activator.CreateInstanceFrom(assemblyName,
type);
object plugin = pluginHandle.Unwrap();
...

// Settings is from the plugin Assembly loaded by the Activator
XmlSerializer x = new XmlSerializer(typeof(Settings));
x.Serialize(settingsFile, _settings);
// blows up here with this exception:

System.InvalidOperationException: There was an error generating the
XML document. ---System.InvalidCastException: Unable to cast object
of type '*.Settings' to type '*.Settings'.
at
Microsoft.Xml.Serialization.GeneratedAssembly.XmlS erializationWriterSettings.Write3_Settings(Object
o)

Which is confusing considering the types are identical. However, when
I add the following XML to App.Config, the error goes away:

<system.diagnostics>
<switches>
<add name="XmlSerialization.Compilation" value="4" />
</switches>
</system.diagnostics>

What am I missing w.r.t. Activator.CreateInstanceFrom and
XmlSerializer?

Thanks.

Moreover, *any* type from a loaded assembly (Assembly.Load,
Assembly.LoadFile, Assembly.LoadFrom, Activator.CreateInstanceFrom)
fails to be serialized/deserialized.

Assembly asm = Assembly.LoadFrom(Path.GetFullPath(assemblyName));
object plugin = asm.CreateInstance(type);
((IPlugin)plugin).WriteSettings(textWriter);

...

public class XmlTest { public string Hello = "Hello World!"; }

public void WriteSettings(TextWriter settingsWriter)
{
XmlSerializer x = new XmlSerializer(typeof(XmlTest));
x.Serialize(settingsWriter, new XmlTest());

}

Once again, if I use the diagnostic switches, everything works fine.

I have found a solution which, while not perfect, works. The assembly
seemingly cannot be loaded from outside the ApplicationBase or
CodeBase or PrivateBinPath. Moving the plugin DLL's to a path
underneath the working directory solved things.

DOES NOT WORK:
\MyExecutable\bin\Debug\MyExecutable.exe
\MyPlugin\bin\Debug\MyPlugin.dll

WORKS:
\MyExecutable\bin\Debug\MyExecutable.exe
\MyExecutable\bin\Debug\Plugins\MyPlugin.dll

However, I'm not entirely sure why the XmlSerializer fails to see
Assemblies loaded from elsewhere. Especially when the diagnostic
switches make it work!