Activators Dotnet 4.6.1 [repack] May 2026

Demystifying .NET Framework 4.6.1 Activators: A Deep Dive into Runtime Instantiation

9. Alternative: Use Activator.CreateInstanceFrom

If your assembly is not loaded yet:

ObjectHandle handle = Activator.CreateInstanceFrom("MyLibrary.dll", "MyNamespace.MyClass");
object instance = handle.Unwrap();

Basic Example (Parameterless Constructor)

Type t = typeof(List<string>);
object list = Activator.CreateInstance(t);
Console.WriteLine(list.GetType().Name); // Output: List`1

The Mechanic of .NET 4.6.1

In the era of .NET 4.6.1, the Activator class acted as the universal mechanic. It was the tool the runtime used to bridge the gap between "knowing of a type" and "having an instance of that type."

The most common method in this story is Activator.CreateInstance. activators dotnet 4.6.1

Here is how the story plays out in code:

3.2 Constructor with Arguments

Type type = typeof(StringBuilder);
object[] args =  "Hello, ", 20 ;
object sb = Activator.CreateInstance(type, args);
// Equivalent to: new StringBuilder("Hello, ", 20)

The .NET 4.6.1 Performance Trick: Activator.CreateInstance(Type) vs Compiled Lambdas

While Activator is convenient, for high-performance scenarios (e.g., creating millions of objects), you should cache a delegate. Demystifying

Solution for .NET 4.6.1: Pre-compiled constructor delegates

public static class ObjectFactory
private static Dictionary<Type, Func<object>> _cache = 
        new Dictionary<Type, Func<object>>();
public static T Create<T>()
Type t = typeof(T);
    if (!_cache.ContainsKey(t))
var ctor = t.GetConstructor(Type.EmptyTypes);
        var lambda = Expression.Lambda<Func<object>>(
            Expression.New(ctor));
        _cache[t] = lambda.Compile();
return (T)_cache[t]();

In .NET 4.6.1, Expression lambdas are significantly faster than repeated Activator.CreateInstance calls. The Mechanic of

2. Key Methods in System.Activator (.NET 4.6.1)

| Method | Description | |--------|-------------| | CreateInstance(Type) | Creates an instance of the specified type using its parameterless constructor. | | CreateInstance(Type, object[]) | Creates an instance using the constructor that best matches the specified arguments. | | CreateInstance<T>() | Generic version; creates an instance of T using the parameterless constructor (requires new() constraint). | | CreateInstanceFrom(string assemblyFile, string typeName) | Loads an assembly file and creates an instance of the named type. | | GetObject(Type) | Creates an instance of a COM object (remoting scenario). |

Note: .NET 4.6.1 does not include ActivatorUtilities (that came with .NET Core / later .NET).