How to return an array back from a function from a LINQ annonymous list

Question

Hi all,

Essentially i want to have a generic function which accepts a LINQ annonymous list and returns an array back. I was hoping to use generics but i just can seem to get it to work.

hopefully the example below helps

say i have a person object with id, fname, lname and dob. i have a generic class with contains a list of objects.

i return an array of persons back

my code snippet wule be something like

dim v = from p in persons.. select p.fname,p.lname

i now have an annonymous type from system.collections.generic.ineumerable(of t)

to bind this to a grid i would have to iterate and add to an array e.g.

dim ar() as array

for each x in v ar.add(x) next

grid.datasource = ar

i dont want to do the iteration continually as i might have different objects

i would like a function which does something like below:

function getArrayList(of T)(dim x as T) as array()

dim ar() as array

for each x in t ar.add(x) next

return ar

end

hope that clairifies. how can i get a generic function with accepts an annonymous list of ienumearable and returns an array back. unfortunately, the one i have does not work.

many thanks in advance as any and all pointers/help will be VASTLY appreciated.

regards

azad

Answer 1

Your question is a little unclear, so I'm not sure how much my answers will help, but here goes...

• An anonymous type has method scope so you cannot return it from a function, at least not in a strongly-typed manner. You can cast to object and then back to a re-creation of your anonymous type, but you'd be better off declaring a simple class with some automatic properties.
• To convert an IEnumerable to an array, just call ToArray()
• However, you can DataBind to an IEnumerable directly, no need to convert it to an array
• If the data you are dealing with can have different fields then you might be best off creating a DataTable and binding that to your DataGrid.

Answer 2

I'm not sure that you can easily pass anonymous objects as parameters, anymore than you can have them as return values.

I say easily, because:

• http://tomasp.net/blog/cannot-return-anonymous-type-from-method.aspx
• http://blog.decarufel.net/2007/11/passing-anonymous-to-and-from-methods.html

[Try the code formatting option on your question (the " button in the editor), it would make it easier to read the parts of your question which are code snippets.]

Answer 3

You'd just call ToArray. Sure, the type is anonymous... but because of type inference, you don't have to say the type's name.

From the example code:

    packages _
    .Select(Function(pkg) pkg.Company) _
    .ToArray()

Company happens to be string, but there's no reason it couldn't be anything else.

Answer 4

You can bind a grid directly to the array of anonymous types. Here's an example:

        var qry = from a in Enumerable.Range(0, 100)
                  select new { SomeField1 = a, SomeField2 = a * 2, SomeField3 = a * 3 };
        object[] objs = qry.ToArray();
        dataGridView1.DataSource = objs;

Note also the call to ToArray, which eliminates the need for a loop. I also assign it to a type of object[] to demonstrate that you could pass that around as its type if you want.