Let's make our anonymous objects easier to copy using the with expression!

Current Implementation

Introduced in C# 9.0, the with keyword was designed to create record objects from other record objects in a non-destructive manner; that is, create a copy of a record and change one or more properties.

public record Animal (string Name, string Type, int Age); 

var dog = new Animal("Charlie", "Dog", 7);

var cat = dog with { Type = "Cat" };

Console.WriteLine(cat.Name); //Charlie

However, we could not do this with anonymous objects. Imagine we have the following:

var dog = new { Name = "Max", Type = "Dog", Age = 10 };

Now imagine we want to create a new anonymous object, with the same properties, using the existing one as a template. We would need to do this in a roundabout fashion:

var cat = new { dog.Name, Type = "Cat", dog.Age };

New Implementation

In C# 10, we can now use the with keyword to create the new anonymous object from the old one, in a more concise way:

var dog = new { Name = "Max", Type = "Dog", Age = 10 };

var cat = dog with { Type = "Cat" };

In essence, the with keyword now functions in the same manner on both record objects and anonymous objects.

Demo Project

Although it won't compile (as of publishing time), I have included a sample of how this feature might work in the demo project for this series:

GitHub - exceptionnotfound/CSharp10Features
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Happy Coding!