Activator.CreateInstance in C# – A Quick Rundown

Activator.CreateInstance in C# is one of the main tools we have when it comes to reflection in C#. This article is a quick look at how we can leverage Activator.CreateInstance as a brief primer on using reflection within C#.

What’s In This Article: Activator.CreateInstance in C#

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What Is Activator.CreateInstance?

Now, let’s explore Activator.CreateInstance and understand how it enables dynamic object creation. The Activator class is a part of the System namespace in C# and provides methods for creating instances of types. The CreateInstance method specifically allows us to create an instance of a type without having to declare it explicitly in code.

How To Use Activator.CreateInstance?

To use Activator.CreateInstance, we first need to specify the type we want to create an instance of. We can pass either the type name or a Type object representing the type we want to instantiate. Additionally, if the type requires constructor arguments, we can pass them as parameters to CreateInstance.

Let’s consider a simple example where we have a class named Person with properties like Name and Age. We can dynamically create an instance of this class using Activator.CreateInstance as follows:

Type personType = typeof(Person);
object personInstance = Activator.CreateInstance(personType);

In the above code snippet, we obtain the Type object for the Person class using the typeof operator. Then, we pass this type to Activator.CreateInstance, which returns an object instance of the Person class.

Handling Constructor Arguments with Activator.CreateInstance

Often, classes require constructor arguments for their instantiation. We can handle this scenario by passing the required arguments to Activator.CreateInstance. Let’s extend our previous example to include a parameterized constructor in the Person class:

public class Person
    public string Name { get; set; }
    public int Age { get; set; }

    public Person(string name, int age)
        Name = name;
        Age = age;

Now, when creating an instance of Person using Activator.CreateInstance, we need to supply the necessary constructor arguments:

Type personType = typeof(Person);
object personInstance = Activator.CreateInstance(personType, "John Doe", 30);

In this case, we provide the arguments "John Doe" and 30 to CreateInstance, which will be used by the constructor of the Person class to initialize the properties.

Quick Recap on Activator.CreateInstance in C#

Activator.CreateInstance is a helpful tool that we have access to when it comes to reflection in C#. We looked at a quick set of simple code examples that show us how to create objects and pass parameters in the constructors.

Reflection in C# is a powerful tool — but it’s easy to abuse. Activator.CreateInstance opens up new possibilities for creating flexible and extensible code, allowing for dynamic object creation and manipulation. By leveraging reflection properly (i.e. without overdoing it at every possible opportunity) in your projects, you can build some really cool things. It allows you to create objects on the fly, based on runtime information, and opens up opportunities for more dynamic systems — like leveraging plugins!

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    Frequently Asked Questions: Activator.CreateInstance

    How can I use reflection in C#?

    To use reflection in C#, you can leverage the System.Reflection namespace, which provides classes and methods for inspecting and manipulating types, members, and assemblies.

    What is Activator.CreateInstance in C#?

    Activator.CreateInstance is a method in C# that dynamically creates instances of types defined at runtime, based on the provided type information.

    When should I use Activator.CreateInstance?

    You can use Activator.CreateInstance when you want to create instances of types dynamically, without knowing their exact type names at compile-time. It is commonly used in scenarios like plugin systems, dependency injection, or generic algorithms.

    author avatar
    Nick Cosentino Principal Software Engineering Manager
    Principal Software Engineering Manager at Microsoft. Views are my own.

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