Exploring the ExpandoObject in C#

Welcome to our blog post on the ExpandoObject in C#! In this article, we will dive into the concept of the ExpandoObject and explore how it can be used in C# programming.

What is the ExpandoObject?

The ExpandoObject is a dynamic object type introduced in C# that allows you to add and remove members at runtime. It is part of the System.Dynamic namespace and provides a flexible way to work with objects that can have dynamic properties.

Unlike traditional objects in C#, which have a fixed set of properties defined at compile-time, the ExpandoObject allows you to dynamically add properties and methods to an object as needed. This can be particularly useful in scenarios where you need to work with data that has a varying structure or when you want to create objects on the fly without defining a specific class.

Creating an ExpandoObject

Creating an ExpandoObject is straightforward. You can instantiate it using the ExpandoObject() constructor:

dynamic expando = new ExpandoObject();

Once you have an instance of the ExpandoObject, you can start adding properties and methods to it:

expando.Name = "John";
expando.Age = 30;
expando.SayHello = new Action(() => Console.WriteLine("Hello, I'm " + expando.Name));

In the example above, we add three properties to the ExpandoObject: Name, Age, and SayHello. The SayHello property is assigned an anonymous method that prints a greeting using the Name property.

Working with ExpandoObject

Since the ExpandoObject is dynamic, you can access its properties and methods using the dot notation:

Console.WriteLine(expando.Name); // Output: John
Console.WriteLine(expando.Age); // Output: 30
expando.SayHello(); // Output: Hello, I'm John

You can also modify or remove properties at runtime:

expando.Name = "Jane";
Console.WriteLine(expando.Name); // Output: Jane

expando.Age = null;
Console.WriteLine(expando.Age); // Output: null

expando.SayHello = null;
expando.SayHello(); // Throws a RuntimeBinderException

As you can see, you can change the value of properties or set them to null. However, if you try to access a property that has been set to null or remove a method that no longer exists, it will result in a RuntimeBinderException.

Using ExpandoObject in Practical Scenarios

The ExpandoObject can be handy in various scenarios, such as:

  • Working with data from external sources, like JSON or XML, where the structure may vary.
  • Creating dynamic APIs or scripting engines.
  • Implementing dynamic configuration settings.
  • Building dynamic user interfaces.

By using the ExpandoObject, you can dynamically shape your objects based on the requirements of your application, providing flexibility and adaptability.


The ExpandoObject in C# is a powerful tool that allows you to work with dynamic objects, adding and removing properties and methods at runtime. It provides flexibility and adaptability, making it a valuable asset in various scenarios. Whether you’re working with external data sources, creating dynamic APIs, or building dynamic user interfaces, the ExpandoObject can help you achieve your goals.

We hope this article has given you a good understanding of the ExpandoObject in C#. Happy coding!

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