Looking for objects that implement an interface from a loaded assembly - how to compare types?
I have a class that will load all assemblies into a directory and then get all types that see if they implement the interface. I can't seem to get the type comparison to work. In the debugger, I can see that my type is loaded (the one I'm interested in) if the comparison always fails. If I use the same comparison code locally, no problem, I get the expected result. I could just compare sting to type interfaces, but I would rather know what I am doing wrong.
Tests:
// Fails
[Fact]
public void FindISerialPortTest()
{
var path = Directory.GetCurrentDirectory();
var results = FindImplementers.GetInterfaceImplementor<ISerialPort>(path);
results.Length.Should().Be(1);
results[0].Should().BeAssignableTo<SerialPortWrapper>();
}
//Passes
[Fact]
public void DoesTypeImplementInterfaceTest()
{
var myType = typeof(SerialPortWrapper);
var myInterface = typeof(ISerialPort);
FindImplementers.DoesTypeImplementInterface(myType, myInterface).Should().Be(true);
}
Class:
public class FindImplementers
{
public static T[] GetInterfaceImplementor<T>(string directory)
{
if (String.IsNullOrEmpty(directory)) { return null; } //sanity check
DirectoryInfo info = new DirectoryInfo(directory);
if (!info.Exists) { return null; } //make sure directory exists
var implementors = new List<T>();
foreach (FileInfo file in info.GetFiles("*.dll")) //loop through all dll files in directory
{
Assembly currentAssembly = null;
Type[] types = null;
try
{
//using Reflection, load Assembly into memory from disk
currentAssembly = Assembly.LoadFile(file.FullName);
types = currentAssembly.GetTypes();
}
catch (Exception ex)
{
//ignore errors
continue;
}
foreach (Type type in types)
{
if (!DoesTypeImplementInterface(type, typeof(T)))
{
continue;
}
//Create instance of class that implements T and cast it to type
var plugin = (T)Activator.CreateInstance(type);
implementors.Add(plugin);
}
}
return implementors.ToArray();
}
public static bool DoesTypeImplementInterface(Type type, Type interfaceType)
{
return (type != interfaceType && interfaceType.IsAssignableFrom(type));
}
}
+3
source to share
1 answer
OK - this gave me the answer: invalidcastexception-when-using-assembly-loadfile
Here's the updated class:
public class PluginLoader
{
public static T[] GetInterfaceImplementor<T>(string directory)
{
if (String.IsNullOrEmpty(directory)) { return null; } //sanity check
DirectoryInfo info = new DirectoryInfo(directory);
if (!info.Exists) { return null; } //make sure directory exists
var implementors = new List<T>();
foreach (FileInfo file in info.GetFiles("*.dll")) //loop through all dll files in directory
{
Assembly currentAssembly = null;
try
{
var name = AssemblyName.GetAssemblyName(file.FullName);
currentAssembly = Assembly.Load(name);
}
catch (Exception ex)
{
continue;
}
currentAssembly.GetTypes()
.Where(t => t != typeof(T) && typeof(T).IsAssignableFrom(t))
.ToList()
.ForEach(x => implementors.Add((T)Activator.CreateInstance(x)));
}
return implementors.ToArray();
}
}
+6
source to share