Creating anonymous types based on lambda expression

Question

I'm trying to create a Fluent Interface to the Winforms Datagrid. This should allow me to use a typed datasource and easy use of properties of properties (Order.Custom.FullName)

I'm adding the columns on initialization and trying to set the property to use there:

dgv.With<Order>().Column("Client Name").On(x => x.Client.FullName);

The original question then poses itself when setting the Datasource:

dgv.SetTypedDatasource<T>(IList<Order> orders)

A big problem here is that Generic Controls are not possible (I guess), so that T cannot be specified for the class, but has to be specified per method...

I want to create a list of anonymous types, based on a given property in a lambda expression:

something like:

ProcessList<Client>(clientList, x => x.FullName);

Is it possible to do something like this:

[Edit] Note that in practice, the expressions will be set earlier, and will be fetched elsewhere...

public void ProcessList<T>(IList<T> sourceList, Expression<Func<T, object>> expression)
{
    var list =
        (from T x
         in sourceList
         select new { expression })
         .ToList();

    // process list ....  grid.DataSource = list;
}

So, I would like to create anonymous types based on the given expression. I know I can evaluate that expression to retrieve the correct properties.

I'm kinda stuck, is something like this possible?

Any ideas?

I am not quite sure, what do you want in your anonymous type ? — driis
– driis, Commented Apr 16, 2009 at 20:28

Jon Skeet · Accepted Answer · 2009-04-16 20:30:15Z

4

Well, with a simple call to Select you can come very close:

ProcessList(clientList.Select(x => new { x.FullName }));

...

public void ProcessList<T>(IEnumerable<T> list)
{
    // process list ... T will be an anonymous type by now
    grid.DataSource = list;
}

(That assumes you don't need the original list in ProcessList as well. If you do, move the select into there.)

answered Apr 16, 2009 at 20:30

Jon Skeet

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3 Comments

Marc Gravell Over a year ago

Note that if that is a winform grid, it will need a ToList() - webform grids are happy with IEnumerable, though.

Bertvan Over a year ago

Still, not quite what I need, I'll explain a bit more in the question.

Bertvan Over a year ago

@Marc, yes I forgot that line :)

Marc Gravell · Accepted Answer · 2009-04-16 20:37:17Z

2

isn't that just grid.DataSource = sourceList.AsQueryable().Select(expression).ToList();

Note that it would be better to introduce a second generic, such that the list is typed:

    public static void ProcessList<TSource, TValue>(
        IList<TSource> sourceList,
        Func<TSource, TValue> expression)
    {
        grid.DataSource = sourceList.Select(expression).ToList();
    }

Note I switched from Expression<...> to just Func<...>, as it seemed to serve no purpose.

edited Apr 16, 2009 at 20:37

answered Apr 16, 2009 at 20:31

Marc Gravell

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