Anonymous type collections?

Question

I am looking for best practices for creating collections made from anonymous types.

There are several approaches - this one and most answers on this thread assume th

Answer 1

I stumbled upon this question while looking for a way to create a temporary list of temporary objects. Why would I want to create such a thing? I was looking for a quick way to return JSON for a list of objects made from some values of another object. Here's what I mean.

Suppose I have an Employee class on the server side which looks like the following in C#:

public class Employee
{
          public int Id;
       public int businessGroupId;
       public string title;
       public int positionId;

       public string firstName;
       public string lastName;
       ...
}

Furthermore I have a collection of those objects which I can easily iterate through, something like the following:

List allEmployees  = new List();

Now, I want to return to my calling web page the entire collection of Employees, but I only want the firstName, lastName for each. I want them returned as JSON.

Here's The Important Point

I do not want to return every property in the Employee Object.

I know I can easily create an anonymous type by iterating through the allEmployees collection and building a new object each time.

It would look something like the following:

foreach (Employee e in allEmployees)
{
    var tempObj = new {F_Name=e.firstName, L_Name=e.lastName};
}

What's The Type Of An Anonymous Type? :)

The trick now is that I want an entire collection (List<>)of these anonymous objects. However, I have no way to provide the List a type that I will be using. I cannot create a List allTempObjects = new List();

Or can I?

With dynamic, It Is Possible

I can do the following and it works great:

List allEmployees  = new List();

foreach (Employee e in allEmployees)
{
           var tempObj = new {F_Name=e.firstName, L_Name=e.lastName};
        allEmployees.Add(tempObj);
}

// use the JavaScript Serializer to serialize the dynamic collection
JavaScriptSerializer jss = new JavaScriptSerializer();
// write the result out to the HTTP Stream (HtmlTextWriter in overridden Render method)

 writer.Write(jss.Serialize(allEmployees));

You will see JSON on the client side which looks like the following:

[
    {
      F_Name: "Seth",
      L_Name: "Godin"
    },
    {
       F_Name: "Charles",
       L_Name: "Petzold"
    },
    {
       F_Name: "Jeff",
       L_Name: "Prosise"
    }
]

Finally, you may question why I want to do this. The simple answer is that I want to new type which is only used to serialize to send to my client. A great reason for an anonymous type and an anonymous collection of anonymous types, don't you think?