C# 4.0 Pocket Reference, 3rd Edition

Anonymous Types

An anonymous type is a simple class created on the fly to store a set of values. To create an anonymous type, you use the new keyword followed by an object initializer, specifying the properties and values the type will contain. For example:

var dude = new { Name = "Bob", Age = 1 };

The compiler resolves this by writing a private nested type with read-only properties for Name (type string) and Age (type int). You must use the var keyword to reference an anonymous type, because the type’s name is compiler-generated.

The property name of an anonymous type can be inferred from an expression that is itself an identifier. For example:

int Age = 1;
var dude = new { Name = "Bob", Age };

is equivalent to:

var dude = new { Name = "Bob", Age = Age };

You can create arrays of anonymous types as follows:

var dudes = new[]
{
  new { Name = "Bob", Age = 30 },
  new { Name = "Mary", Age = 40 }
};

Anonymous types are used primarily when writing LINQ queries.