ExpandoObject vs. Dictionary: When Does Dynamic Property Assignment Offer Real Advantages?

The True Benefits of ExpandoObject

Introduction

The ExpandoObject class introduced in .NET 4 allows developers to dynamically assign properties to objects at runtime. This has led to questions about its advantages over traditional dictionary structures.

Syntactic Sugar

While ExpandoObject may appear to enhance syntax by simplifying property access, it offers no significant functional benefits over dictionaries. The following code:

dynamic obj = new ExpandoObject();
obj.MyInt = 3;
obj.MyString = "Foo";
Console.WriteLine(obj.MyString);

Is essentially equivalent to:

var obj = new Dictionary<string, object>();
obj["MyInt"] = 3;
obj["MyString"] = "Foo";

Console.WriteLine(obj["MyString"]);

Hierarchical Object Representation

One potential advantage of ExpandoObject lies in its ability to create complex hierarchical objects. For instance:

Dictionary<String, object> dict = new Dictionary<string, object>();
Dictionary<String, object> address = new Dictionary<string,object>();
dict["Address"] = address;
address["State"] = "WA";
Console.WriteLine(((Dictionary<string,object>)dict["Address"])["State"]);

This code becomes significantly more legible with ExpandoObject:

dynamic expando = new ExpandoObject();
expando.Address = new ExpandoObject();
expando.Address.State = "WA";
Console.WriteLine(expando.Address.State);

Event Handling and Property Notification

ExpandoObject implements the INotifyPropertyChanged interface, granting greater control over properties compared to dictionaries. Additionally, events can be added to ExpandoObject, enabling dynamic event handling.

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