C# 如何将 Poco 转换为 List<poco> 不知道你使用的是哪个 poco</poco>

Question

I've got a method that accepts any POCO. The method then needs to be able to check to see if the POCO is a List<Poco> . If it's not a list, it needs to convert it to a list.

Example

MyCustomMethod(object input)
{
    // if !input is list
    // convert input to list
}

And I would call it as such

MyCustomMethod(Pocos.foo);
MyCustomMethod(Pocos.bar);

Remember MyCustomMethod has no idea what poco is being sent to it. All it knows is to check if the object is a list, and if it's not, it needs to convert it to a list of that same object.

What would be the easiest way to approach this?

EDIT:

Some reasoning for this might help. I'm building a sencha-touch app, and the Ext.Data.Store requires all JSON data to be in an array.

I'm building my WebService using asp.net-mvc-3 and I've got a custom JsonPResult . The JsonPResult accepts any object and returns that object as JsonP. If I'm sending a list to the JsonPResult, everything is gravy. If I'm just sending a single object, Sencha Touch pukes until I put that object into an array.

In order to keep things DRY, I'd like the JsonPResult to check if any object is a list, and do the work, rather than repeating myself in every controller.

Answer 1

You could do a safe cast:

var list = obj as List<Poco>;
if (list != null)
   // It's a list and you now have a reference
else
    list = new List<Poco> { (Poco)obj };

Edit to support any POCO, you'll need to use generics, so here is a generic extension method for you:

public static IList<T> AsList<T>(this T item)
{
    var list = item as List<T>;
    if (list != null)
        return list;

    return new List<T>() { item };
}

And some examples:

string name = "Matt";
var list = name.AsList();

List<string> names= new List<string>() { "Matt" };
var list2 = names.AsList();

Both list and list2 will be lists of strings, but in the second instance, it has returned the casted list directly, instead of creating a new one and inserting itself into it. Type inference takes care of the generic argument, and it can be applied to any type.