How to Dynamically Add C# Properties at Runtime Using ExpandoObject and DynamicObject?

How to Dynamically Add C# Properties at Runtime

Introduction

Adding properties dynamically at runtime is a common requirement in various programming scenarios. While approaches like using Dictionaries or Collections can suffice in certain situations, they may not be suitable for all use cases. Let's explore an alternative solution leveraging ExpandoObject.

Using ExpandoObject

ExpandoObject is a built-in class in .NET that allows you to add and remove members dynamically at runtime, enabling the assignment and retrieval of values through standard dot syntax. This approach provides a convenient way to create dynamic objects with properties that are determined on the fly.

To use ExpandoObject, you can simply create a new instance and assign properties as needed:

dynamic dynObject = new ExpandoObject();
dynObject.SomeDynamicProperty = "Hello!";

Customizing Dynamic Object Behavior

If you have specific requirements for how your dynamic object behaves, you can extend the DynamicObject class and implement custom logic for handling member access and modification. Here's an example:

sealed class MyDynObject : DynamicObject
{
    private readonly Dictionary<string, object> _properties;
    public MyDynObject(Dictionary<string, object> properties) { _properties = properties; }

    public override IEnumerable<string> GetDynamicMemberNames() { return _properties.Keys; }
    public override bool TryGetMember(GetMemberBinder binder, out object result) {
        return _properties.TryGetValue(binder.Name, out result); }
    public override bool TrySetMember(SetMemberBinder binder, object value) {
        _properties[binder.Name] = value; return true; }
}

With this custom dynamic object, you can create dynamic objects with properties and modify them dynamically at runtime:

var dyn = GetDynamicObject(new Dictionary<string, object>() { { "prop1", 12 } });
Console.WriteLine(dyn.prop1);
dyn.prop1 = 150;

Considerations

While using DynamicObject provides flexibility and ease of use, it also introduces some potential downsides:

• Runtime Verification: The compiler cannot verify dynamic calls, so there is potential for runtime errors and reduced debugging capabilities.
• Intellisense Support: Dynamic objects do not provide intellisense support in development environments, making it harder to navigate and explore the available properties at runtime.

Therefore, it's essential to balance the benefits of dynamic object manipulation with these considerations when choosing the most suitable approach for your development needs.

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