CODEWITHSUNDEEP
c#reflection
David
David

Reputation: 16120

How to load a type from the type's name and the assembly's name

I need to get an instance of a type whose name and assembly name I will have at runtime. I know in advance the type will have a parameterless constructor. What's the easiest way to do this?

It's waaaaaaay harder than I was hoping it would be.

Edit: I'm not if this is relevant, but the assembly will be referenced. I don't need to load it from disk or something.

Upvotes: 6

Views: 9015

Answers (7)

Boaz
Boaz

Reputation: 4669

Activator.CreateInstance(Type.GetType("System.Int32"));

Activator

Type

Upvotes: 2

Jeremy McGee
Jeremy McGee

Reputation: 25200

Here's something that works using the fancy dynamic keyword. You'll need to reference the other class for the test to pass, or use a build event to copy over the built DLL.

namespace TestLibrary
{
    [TestFixture]
    public class Tests
    {
        [Test]
        public void FileCheck()
        {
            dynamic otherClass = 
                AppDomain.CurrentDomain.CreateInstanceFromAndUnwrap("OtherLibrary.dll",                
                    "Prefix.OtherLibrary.SomeClass");
            otherClass.SayHello();   // look, ma! no casting or interfaces!
        }
    }
}

namespace Prefix.OtherLibrary
{
    public class SomeClass
    {
        public void SayHello()
        {
            Console.WriteLine("Hello, world.");
        }
    }
}

Unlike Activator, AppDomain.CurrentDomain.CreateInstanceFromAndUnwrap takes a filename as the first argument rather than a type specifier. This is sometimes useful, especially when you don't care about the strong name of the assembly.

Upvotes: 1

dtb
dtb

Reputation: 217313

From MSDN:

Activator.CreateInstance Method (String, String)

Creates an instance of the type whose name is specified, using the named assembly and default constructor.

public static ObjectHandle CreateInstance(
  string assemblyName,
  string typeName
)

Example:

var assemblyName =
    "System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089";

var typeName = "System.Net.WebClient";

var instance = Activator.CreateInstance(assemblyName, typeName).Unwrap();

Upvotes: 5

Simon Mourier
Simon Mourier

Reputation: 138960

If referencing System.Web.dll is not an issue for you, there is the little-known BuildManager.GetType Method which is quite efficient. It does not even requires the assembly name because it scans for types in assemblies in the current AppDomain execution path.

So the code would be:

object instance = Activator.CreateInstance(BuildManager.GetType("MyNamespace.MyClass", true));

Upvotes: 3

vc 74
vc 74

Reputation: 38179

Type referencedType = typeof(AReferencedType);
AReferencedType instance = Activator.CreateInstance<AReferencedType>();

or 

Type type = Type.GetType("Type's full name");
object instance = Activator.CreateInstance(type);

Upvotes: 2

Jakub Konecki
Jakub Konecki

Reputation: 46008

Type.GetType(string.Concat(typeName, ", ", assemblyName))

http://msdn.microsoft.com/en-us/library/w3f99sx1.aspx http://msdn.microsoft.com/en-us/library/system.type.assemblyqualifiedname.aspx

Upvotes: 8

Rich O&#39;Kelly
Rich O&#39;Kelly

Reputation: 41767

The following should suffice:

var assmebly = Assembly.Load("FullyQualifiedAssemblyName");
var type = assmebly.GetType("FullTypeName");
var instance = Activator.CreateInstance(type);

Upvotes: 2

Related Questions