Return a List without a certain property using Linq in c#?

Question

I have an object containing different properties like the object below:

 public class CompressedLogResponse
 {
    public string LoggerType { get; set; }
    public int NumberOfRegisters { get; set; }
    public int NewLogId { get; set; }
    public DateTime LoggerAnnounceTime { get; set; }
    public List<Log> Log{ get; set; }
 }

How can I return a List of this objekt that does not include the List<Log> Log property?

Linq would be preffered

Thanks for any help that you can provide

All the objects on this class have that property. Do you mean ones with a null or empty `Log` list? — Enigmativity, Oct 29 '14 at 11:01
You couldn't return a List of CompressedLogResponse without the Log property. You could return an anonymous type without that property though. — Steve, Oct 29 '14 at 11:01
By "does not include", I understand all the properties excluding the List. By using the original list, and creating a list of anonymous types with it and removing the unwanted property - I think the OP would get the desired result. — Mez, Oct 29 '14 at 11:08
Why are you wanting to do this? There are a number of ways to ignore the Log property but how is the CompressedLogResponse having a List causing you a problem? — AlexC, Oct 29 '14 at 11:09
When you say "return" do you mean that you want to return the list to someone calling your function? — Sean, Oct 29 '14 at 11:18
This is possible if you are using .NET 4.0 and above, as I showed in my answer. — Mez, Oct 29 '14 at 12:13

score 0 · Answer 1 · edited May 23 '17 at 12:13

0

You can return an anonymous list of your original list like the following;

public static List<dynamic>   Test() {

            List<CompressedLogResponse> list = new List<CompressedLogResponse>();

            var result = list.Select(x => new
            { 
                x.LoggerAnnounceTime,
                x.LoggerType,
                x.NewLogId,
                x.NumberOfRegisters
            });

            return result.ToList<dynamic>();
        }

Take a look at the .Select(), and also the dynamic keyword.

Then to call it,

var x =  Test();
       foreach(dynamic o in x)
       {
           int NumberOfRegisters;

           //You have 2 ways... either by
           NumberOfRegisters = o.NumberOfRegisters;

           // or reflection
           NumberOfRegisters = o.GetType().GetProperty("NumberOfRegisters").GetValue(o, null);

       }

edited May 23 '17 at 12:13

Community

1
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answered Oct 29 '14 at 11:03

Mez

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That won't work if you need to return `result` to a caller as the type held by the list is anonymous. – Sean Oct 29 '14 at 11:20
We don't have enough information from the OP if it's going to be used outside our current context. What we do know is that List is not required, and we'd prefer to use Linq. – Mez Oct 29 '14 at 11:25
you are talking from returning the list. Maybe what your talking about is, selecting an anonymous list. Returning anonymous types is not possible. – Dom84 Oct 29 '14 at 11:50
Why would i wan't to use dynamic in that context? – quadroid Oct 29 '14 at 12:22
In the context of returning a list of anonymous types, @Console. – Mez Oct 29 '14 at 12:24
@Mez ok you're right, haven't thougth about that, because i never used it before. – Dom84 Oct 29 '14 at 13:40

score 0 · Answer 2 · answered Oct 29 '14 at 11:09

whith "does not include the List Log property" i guess you mean that the property "public List Log" will be blanked but still there, so you can just null that property out, because if you create an object that doesn't contain the "public List Log" property, than it will not be a "CompressedLogResponse" but will be another type.

List<CompressedLogResponse> listOne = new List<CompressedLogResponse>();
//....
//fill the listOne
//....
List<CompressedLogResponse> listWithoutListLog = (from item in listOne
                                      select new CompressedLogResponse(
                                            LoggerType = item.LoggerType,
                                            NumberOfRegisters = item.NumberOfRegisters ,
                                            NewLogId = item.NewLogId ,
                                            LoggerAnnounceTime = item.LoggerAnnounceTime ,
                                            Log= null)).ToList();

score 0 · Accepted Answer · answered Oct 29 '14 at 12:39

You cannot just hide a property of a class (you declared it a as public)

Option 1: Althought as Robson wrote you can set it null (thats not very reliable thaught cause nobody expects a class containing a property that is always null)

Option2: If you consume the class on the same place use a anonymous type as Mez wrote, althought it sounds like you want to hide the Property from external usage. (I don't like the dynamic approach, the dynamic keyword was made for interop/DOM not for transporting anonymous types.)

Option3: If you want a List of this type to be returned without the Log property, you have to create a new class (Inheritance is a good way to realize this):

public class CompressedLogResponseBase
{
    public string LoggerType { get; set; }
    public int NumberOfRegisters { get; set; }
    public int NewLogId { get; set; }
    public DateTime LoggerAnnounceTime { get; set; }
}

public class CompressedLogResponse : CompressedLogResponseBase
{
    public List<Log> Log{ get; set; }
}

Now you can return a list of base items (that do not have a Log property at all)

public List<CompressedLogResponseBase> ReturnWithoutLog(IEnumerable<CompressedLogResponse> items)
{
    return ((IEnumerable<CompressedLogResponseBase>)items).ToList();
}

If a IEnumerable as return type is suficient it becomes really easy

public IEnumerable<CompressedLogResponseBase> ReturnWithoutLog(IEnumerable<CompressedLogResponse> items)
{
    return items
}

Return a List without a certain property using Linq in c#?

3 Answers3