Find Types in All Assemblies

I need to look for specific types in all assemblies in a web site or windows app, is there an easy way to do this? Like how the controller factory for ASP.NET MVC looks across all assemblies for controllers.

Thanks.

Answers


There are two steps to achieve this:

  • The AppDomain.CurrentDomain.GetAssemblies() gives you all assemblies loaded in the current application domain.
  • The Assembly class provides a GetTypes() method to retrieve all types within that particular assembly.

Hence your code might look like this:

foreach (Assembly a in AppDomain.CurrentDomain.GetAssemblies())
{
    foreach (Type t in a.GetTypes())
    {
        // ... do something with 't' ...
    }
}

To look for specific types (e.g. implementing a given interface, inheriting from a common ancestor or whatever) you'll have to filter-out the results. In case you need to do that on multiple places in your application it's a good idea to build a helper class providing different options. For example, I've commonly applied namespace prefix filters, interface implementation filters, and inheritance filters.

For detailed documentation have a look into MSDN here and here.


Easy using Linq:

IEnumerable<Type> types =
            from a in AppDomain.CurrentDomain.GetAssemblies()
            from t in a.GetTypes()
            select t;

foreach(Type t in types)
{
    ...
}

LINQ solution with check to see if the assembly is dynamic:

/// <summary>
/// Looks in all loaded assemblies for the given type.
/// </summary>
/// <param name="fullName">
/// The full name of the type.
/// </param>
/// <returns>
/// The <see cref="Type"/> found; null if not found.
/// </returns>
private static Type FindType(string fullName)
{
    return
        AppDomain.CurrentDomain.GetAssemblies()
            .Where(a => !a.IsDynamic)
            .SelectMany(a => a.GetTypes())
            .FirstOrDefault(t => t.FullName.Equals(fullName));
}

Most commonly you're only interested in the assemblies that are visible from the outside. Therefor you need to call GetExportedTypes() But besides that a ReflectionTypeLoadException can be thrown. The following code takes care of these situations.

public static IEnumerable<Type> FindTypes(Func<Type, bool> predicate)
{
    if (predicate == null)
        throw new ArgumentNullException(nameof(predicate));

    foreach (var assembly in AppDomain.CurrentDomain.GetAssemblies())
    {
        if (!assembly.IsDynamic)
        {
            Type[] exportedTypes = null;
            try
            {
                exportedTypes = assembly.GetExportedTypes();
            }
            catch (ReflectionTypeLoadException e)
            {
                exportedTypes = e.Types;
            }

            if (exportedTypes != null)
            {
                foreach (var type in exportedTypes)
                {
                    if (predicate(type))
                        yield return type;
                }
            }
        }
    }
}

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