How to use Expression to build an Anonymous Type?

In C# 3.0 you can use Expression to create a class with the following syntax:

var exp = Expression.New(typeof(MyClass));
var lambda = LambdaExpression.Lambda(exp);
object myObj = lambda.Compile().DynamicInvoke();

But how do you use Expression to create an Anonymous class?

//anonymousType = typeof(new{ Name="abc", Num=123});
Type anonymousType = Expression.NewAnonymousType???  <--How to do ?
var exp = Expression.New(anonymousType);
var lambda = LambdaExpression.Lambda(exp);
object myObj = lambda.Compile().DynamicInvoke();