When getting types from an assembly, is there a way to determine if type is an Anonymous Type? - vb.net

Question

I added an Anonymous type to my project:
'Put the courses from the XML file in an Anonymous Type
Dim courses = From myCourse In xDoc.Descendants("Course")
Select New With
{
.StateCode = myCourse.Element("StateCode").Value, _
.Description = myCourse.Element("Description").Value, _
.ShortName = myCourse.Element("ShortName").Value, _
.LongName = myCourse.Element("LongName").Value, _
.Type = myCourse.Element("Type").Value, _
.CipCode = CType(myCourse.Element("CIPCode"), String) _
}
For Each course In courses
If Not UpdateSDECourseCode(acadYear, course.StateCode, course.Description, course.Type, course.ShortName, course.LongName, course.CipCode) Then errors.Add(String.Format("Cannot import State Course Number {0} with Year {1} ", course.StateCode, acadYear))
Next
After doing so, a Unit Test failed:
Public Function GetAreaTypeList() As List(Of Type)
Dim types As New List(Of Type)
Dim asmPath As String = IO.Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "My.Stuff.dll")
For Each t As Type In Reflection.Assembly.LoadFrom(asmPath).GetTypes()
If t.Namespace.StartsWith("My.Stuff.BatchUpdater") Then
If t.BaseType Is GetType(My.Stuff.BatchUpdater.Area) Then
types.Add(t)
End If
End If
Next
Return types
End Function
It fails because a new type has been added to the project (VB$AnonymousType_0`6) and it does not have a property called Namespace.
I fixed by making the following change to the IF Statement:
If Not t.Namespace Is Nothing AndAlso t.Namespace.StartsWith("My.Stuff.BatchUpdater") Then
Since I don't fully understand what's happening, I feel leery about my code change.
Why is the Namespace Nothing for the Anonymous type?
Would you fix your Unit Test in the same fashion? Or should it be something more specific (e.g. If Not t.Names = "VB$AnonymousType_0`6")
UPDATE
decyclone gave me the info I needed to create a better test:
For Each t As Type In Reflection.Assembly.LoadFrom(asmPath).GetTypes()
'Ignore CompilerGeneratedAttributes (e.g. Anonymous Types)
Dim isCompilerGeneratedAttribute = t.GetCustomAttributes(False).Contains(New System.Runtime.CompilerServices.CompilerGeneratedAttribute())
If Not isCompilerGeneratedAttribute AndAlso t.Namespace.StartsWith("My.Stuff.BatchUpdater") Then
'...Do some things here
End If
Next
Honestly, it could be improved more with a LINQ query, but this suits me.

Answer 1

Anonymous methods and types are decorated with CompilerGeneratedAttribute. You can check for their existance to identify an anonymous type.
var anonymous = new { value = 1 };
Type anonymousType = anonymous.GetType();
var attributes = anonymousType.GetCustomAttributes(typeof(CompilerGeneratedAttribute), false);
if (attributes.Any())
{
// Anonymous
}
You can filter these out in your test.
It is also possible to mark a user defined type with CompilerGeneratedAttribute. So maybe you can combine it with checking if Namespace is null or not
var anonymous = new { value = 1 };
Type anonymousType = anonymous.GetType();
var attributes = anonymousType.GetCustomAttributes(typeof(CompilerGeneratedAttribute), false);
if (attributes.Any() && anonymousType.Namespace == null)
{
// Anonymous
}