Get all User-Created Classes in AppDomain.CurrentDomain

Question

I want to loop over all classes which I have added in my project

Assembly[] foo = AppDomain.CurrentDomain.GetAssemblies();

foreach(Assembly a in foo)
{                
    foreach(Type t in a.GetTypes())
    {

    }
}

this is what I tried but I want to exclude the assemblies which are provided by .net, for example "mscorlib"

Answer 1

One common solution would be to filter the assemblies by name, if all of your assemblies have a common prefix (if you have a more or less unique prefix).

var foo = AppDomain.CurrentDomain.GetAssemblies()
                                 .Where(a=>a.FullName.StartsWith("MyProject."));

If you are only interested in some specific types, consider using attributes for your classes, or even add one at assembly level.

Example:

Create an attribute:

[AttributeUsage(AttributeTargets.Assembly)]
public class MyAssemblyAttribute : Attribute { }

add the following to your AssemblyInfo.cs:

[assembly: MyAssemblyAttribute()]

and filter the assemblies you are looking at:

var foo = AppDomain.CurrentDomain
                   .GetAssemblies()
                   .Where(a => a.GetCustomAttributes(typeof(MyAssemblyAttribute), false).Any());

Also you will find at this question interesting. In one answer it is suggested to check the fully qualified name of each assembly, but this is quite tedious, e.g.:

//add more .Net BCL names as necessary
var systemNames = new HashSet<string>
{
    "mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089",
    "System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"
    ...
};

var isSystemType = systemNames.Contains(objToTest.GetType().Assembly.FullName); 

It's always easier to mark your assemblies (by name or attribute) than trying to identify which ones are part of the .Net framework.

Answer 2

In one of my projects I need a list of classes used as business objects. These classes are always user-created types, but can be in a referenced assembly. They do not implement a specific interface and do not derive from a specific base class and do not have a distinctive attribute.

This is the code I use to filter useful types:

return
    type.IsClass && // I need classes
    !type.IsAbstract && // Must be able to instantiate the class
    !type.IsNestedPrivate && // Nested private types are not accessible
    !type.Assembly.GlobalAssemblyCache && // Excludes most of BCL and third-party classes
    type.Namespace != null && // Yes, it can be null!
    !type.Namespace.StartsWith("System.") && // EF, for instance, is not in the GAC
    !type.Namespace.StartsWith("DevExpress.") && // Exclude third party lib
    !type.Namespace.StartsWith("CySoft.Wff") && // Exclude my own lib
    !type.Namespace.EndsWith(".Migrations") && // Exclude EF migrations stuff
    !type.Namespace.EndsWith(".My") && // Excludes types from VB My.something
    !typeof(Control).IsAssignableFrom(type) && // Excludes Forms and user controls
    type.GetCustomAttribute<CompilerGeneratedAttribute>() == null && // Excl. compiler gen.
    !typeof(IControllerBase).IsAssignableFrom(type); // Specific to my project

Since my user types are not in the GAC !type.Assembly.GlobalAssemblyCache does a pretty good job in excluding most of BCL (Framework libraries) types and some third-party stuff.

This is not watertight, but works well my case. You will most likely need to tweak it for your needs.