Convert ICollection<T> to List<T>

Question

I am trying to convert ICollection to List using below code-

ICollection<DataStructure> list_Stuctures = dataConnectorService.ListStructures(dataConnector, SupportedDataStructures.All);

List<DataStructure> lst_DataStructure = new List<DataStructure>();

list_Stuctures.CopyTo(lst_DataStructure);

On last line, I get below exception-

Exception = TargetParameterCountException

Message = Parameter count mismatch.

How to convert ICollection to List?

Answer 1

The easiest way to convert a ICollection to a List is the usage of LINQ like (MSDN)

List<T> L = C.ToList();

Dont't forget to add

using System.Linq;

otherwise ToList() is not available.

Answer 2

You can supply the collection as an argument in the List<T> constructor:

List<DataStructure> lst_DataStructure = new List<DataStructure>(list_Stuctures);

Or use the .ToList() extension method, which does exactly the same thing.

Answer 3

Keep it simple, ToList:

List<DataStructure> lst_DataStructure = list_Stuctures.ToList();

Answer 4

None of the recommendations worked for me. I'm a bit surprised to not see this pretty obvious answer. At least it seems obvious to me after looking through other attempts. This may be a tab bit longer in some cases, but perhaps worth it for performance and peace of mind?

What do you guys think?

For context

I am working with two different types.

In my case both share the same underlying classes (Integrations are fun I guess).

PLAY - https://dotnetfiddle.net/oTa4Dt#

/// One is ---------- | ---- ICollection<T>
/// The other is ---- | ---- List<PreferencesResponse>

ICollection<T> result = default!;

var myPreferences = new List<PreferencesResponse>();
foreach (var preference in result.Result.ToList())
{
    var preferencesResponse = new PreferencesResponse()
    {
        Id = preference.Id,
        Status = preference.Status,
        StatusDescription = preference.StatusDescription,
        Priority = preference.Priority
    };
    mySupplierPreferences.Add(preferencesResponse);
}
returnValue = new Response(true, mySupplierPreferences);

Are there any reasons you can think of that this wouldn't be correct or at least - most correct?

Answer 5

Because ICollection implement IEnumerable you can use a foreach.

foreach(var item in list_Stuctures) 
{
  lst_DataStructure.ADD(item);
}