I am trying create a WCF Data Services ServiceOperation that does grouping on the server side and then sends the data down to the client.
When I try to call it (or even connect to the service) I get an error. It says that it can't construct an interface.
The only interface I am using is IGrouping.
What is a/the actual class for this interface?
Update:
I checked the type while debugging a sample app and it told me it was:
System.Linq.Lookup<TKey,TElement>.Grouping
But what assembly is it in?
Several types in the BCL implement IGrouping
, however they are all internal and cannot be accessed except by the IGrouping
interface.
But an IGrouping
is merely an IEnumerable<TElement>
with an associated key. You can easily implement an IGrouping
that is backed by a List<TElement>
and that should not be hard to serialize across a call boundary:
public class Grouping<TKey, TElement> : IGrouping<TKey, TElement> {
readonly List<TElement> elements;
public Grouping(IGrouping<TKey, TElement> grouping) {
if (grouping == null)
throw new ArgumentNullException("grouping");
Key = grouping.Key;
elements = grouping.ToList();
}
public TKey Key { get; private set; }
public IEnumerator<TElement> GetEnumerator() {
return this.elements.GetEnumerator();
}
IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }
}
After applying the GroupBy
operator you can create a list of Grouping
instances:
var listOfGroups =
source.GroupBy(x => ...).Select(g => new Grouping<TKey, TElement>(g)).ToList();
Here is probably the most basic and generic implementation of IGrouping. Its constructor takes a key and a set of values.
public class Grouping<TKey, TElement> : IGrouping<TKey, TElement>
{
private readonly TKey key;
private readonly IEnumerable<TElement> values;
public Grouping(TKey key, IEnumerable<TElement> values)
{
if (values == null)
throw new ArgumentNullException("values");
this.key = key;
this.values = values;
}
public TKey Key
{
get { return key; }
}
public IEnumerator<TElement> GetEnumerator()
{
return values.GetEnumerator();
}
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
}
I checked the type with a sample app and it is this:
System.Linq.Lookup<TKey,TElement>.Grouping
. But what assembly is it in?
It's a type nested in System.Linq.Lookup<TKey,TElement>
; internal to the System.Core
assembly.
var groupingType = "1".GroupBy(x => x).Single().GetType().GetGenericTypeDefinition();
Console.WriteLine("Type: " + groupingType);
Console.WriteLine("Public: " + groupingType.IsPublic);
Console.WriteLine("Assembly: " + groupingType.Assembly);
Output:
Type: System.Linq.Lookup`2+Grouping[TKey,TElement]
Public: False
Assembly: System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
As of .NET 4.0, there is no public type in the core .NET framework that implements System.Linq.IGrouping<TKey,TElement>
. If you need such a type (say that's serializable), you'll probably have to roll one yourself, unfortunately.
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With