Activator.CreateInstance

C# course · Advanced · Lesson 45/83

Learn dynamic instantiation with Activator.CreateInstance.

Activator.CreateInstance

Activator.CreateInstance(typeof(T)) instantiates a type at runtime. It returns object; the caller must provide type safety. DI containers, serializers and plugin systems create instances this way.

For parameterized constructors use Activator.CreateInstance(typeof(T), arg1, arg2); the matching constructor is called. When the type is only known at runtime (e.g. from a config file), Activator replaces new.

Parameterized constructors

The call Activator.CreateInstance(typeof(T), 5, "text") finds the constructor whose signature matches and invokes it. The argument count, order and types must match; otherwise a MissingMethodException is thrown.

The result returns as object?; cast to the real type with as or a cast. DI containers use this to resolve dependencies; e.g. Activator.CreateInstance(typeof(MyService), logger).

Exercise Create an instance dynamically and print the type name

Create an instance dynamically with object obj = Activator.CreateInstance(typeof(Sample));. Print obj.GetType().Name with Console.WriteLine.

Show example solution

Create the instance with object obj = Activator.CreateInstance(typeof(Sample));. Print the type name with Console.WriteLine(obj.GetType().Name);.
Example solution:
using System;

class Sample
{
    public string Name { get; set; } = "Test";
}

class Program
{
    static void Main()
    {
        object obj = Activator.CreateInstance(typeof(Sample));
        Console.WriteLine(obj.GetType().Name);
    }
}

Test yourself

Match the method to its purpose

Activator.CreateInstance

Creates an instance
typeof(T)

Gives a Type object
GetType()

Runtime type
GetMethods()

Method list

Complete the CreateInstance call

object obj = Activator.____(typeof(Sample));

Show answer

object obj = Activator.CreateInstance(typeof(Sample));

What does Activator.CreateInstance return?
- An object instance
- A Type object
- A MethodInfo
- null
Show answer

An object instance — Correct. Activator.CreateInstance returns an object instance.

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Activator.CreateInstance