CODEWITHSUNDEEP
c#wcfgeneric-list
Max
Max

Reputation: 4077

wcf inherit from list<T>

I am working on a WCF service in which the objects are defined as below :-

public class Test1
{
 public string s {get;set;}
 public string a {get;set;}
}

public class Test2
{
  public string u {get;set;}
  public string v {get;set;}
}

public class ABC : List<Test1>

public class DEF: List<Test2>

public class Test
{
   public ABC x {get;set;}
   public DEF y {get;set;}
}

The code that raised the exception was (assuming that result is an instance of class ABC) :-

return result.OrderBy(i=>i.s).ThenBy(j=>j.a);

The above code threw me an InvalidCastException on runtime. I am assuming that this happened because OrderBy returned an IOrderedEnumerable and so, it was unable to cast it. I tried various variations of the above code :-

return (ABC)result.OrderBy(i=>i.s).ThenBy(j=>j.a);
return (ABC)result.OrderBy(i=>i.s).ThenBy(j=>j.a).ToList();

None worked. So, I changed the Test class to following :-

public class Test
{
   public List<T> x {get;set;}
   public List<T> y {get;set;}
}

So, everything is working fine now. I read somewhere that we should not use List in public APIs. However, does that apply to WCF also ? And, is this approach correct or should I try to inherit ABC and DEF class from Collection<T> ?

Upvotes: 1

Views: 149

Answers (2)

Lee O.
Lee O.

Reputation: 3322

This will cause an InvalidCastException

List<Test1> test1 = new List<Test1>();
ABC abc = (ABC)test1;

This will not

List<Test1> test1 = new ABC();
ABC abc = (ABC)test1;

What you are doing is the equivalent of the first one. There may be better ways but one solution would be to add a constructor to ABC that takes an IEnumerable.

public class ABC : List<Test1>
{
   public ABC(IEnumerable<Test1> enumerable)
   {
      if (enumerable != null)
         this.AddRange(enumerable);
   }
}

Then change your return statement to look like this.

return new ABC(result.OrderBy(i=>i.s).ThenBy(j=>j.a));

Upvotes: 2

D Stanley
D Stanley

Reputation: 152624

should I try to inherit ABC and DEF class from Collection<T>

Only if ABC and DEF offer functionality above what List<T> provides. Even then, extension methods may be more appropriate.

But it's unclear why you're getting an InvalidCastException - You need to add the code that gives you that exception to know what a proper solution is.

Upvotes: 0

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