Determining if a generic Type implements ICollection

Determining if a generic Type implements ICollection

• Edentheguy

  Hi,

  I am not concerned about the compile time List<string> class at all. Nothing about my post referred to compile time. I am in fact attempting to interrogate the generic class structure at runtime using reflection.

  I am trying to establish the relationship between List<T> and IList<T> at runtime, which is certainly possible. My only caveat is that I am attempting to obtain information about this relationship without necessarily knowing the type of T. I have a parent object that contains properties that contain lists of child objects. I am attempting to find which of the parent properties refer to collections of child objects. All I need to know to obtain this information is that the parent property is one of several pre-determined collection types, namely IList, ITypedList, IEnumerable. I have started with IList. I would like to know which of the properties expose IList derivatives. Generic types are available for interrogation at runtime, and there is almost certainly a way to do this. I am sure someone out there will have some additional suggestions.

  You have missed my question completely.

  Kind Regards

  Craig

  
  

• R.Arjun

  Generics is a runtime feature - code for a class containing the actual types is JIT-ted at runtime. For example, when you instantiate a list like this:
  
  public List<string> listOfStrings = new List<string>();
  
  Simply put, a list class with T replaced with string is JIT compiled at runtime when this code is called.
  Because of this, you will not have a type representing List of strings at compile-time, and you will thus have no type at compile-time.
  
  I'm afraid the closest you can get to seeing what is inside your list, is by calling GetType() in the instance - you will see something like
  
  System.Collections.Generic.List`1[System.String]
  
  
  
  
  

• Manoj Kumar Goud

  I am supprised that with a generic you cannot obtain Type information of T without having to first create it or pass in Type into a routine like I am having to do here.

  public class EnvDTEToolWindowController<T> : EnvDTEClass

  {

  ...

  public bool ShowToolWindow(Type toolWindowType, string toolWindowCaption, string toolWindowGUID)

  {

  if (toolWindowType == null)

  throw new ArgumentNullException("toolWindowType");

  Type userControl = this.Env.GetType("System.Windows.Forms.UserControl");

  if (userControl == null)

  throw new NullReferenceException("userControl is null");

  if (!toolWindowType.IsSubclassOf(userControl))

  throw new Exception("toolWindowType must be of System.Windows.Forms.UserControl Type");

  Please put it on the wish list

  Kenneth

  
  
  

• Greg Allen

  Check if the type returned by propertyInfo.PropertyType.GetGenericTypeDefinition() implements ICollection<T>.

  
  
  

• Anand Raman - MSFT

  Hi Mattias,

  Further to my last post, the object being in the incorrect state was my mistake.

  You are correct. The following assertion is true, I am able to test the collection with the following code.

  Type.GetType("System.Collections.Generic.IList`1").Equals(pi.PropertyType.GetGenericTypeDefinition());

  
  

• Nagu

  James, that relies on compile time overload resolution. It won't help when working with reflection at runtime.

  
  
  

• Michael Collins

  A variation of this should work for you:

  class ABC : List<string> {} public class MyClass { public void Code(string[] args) { ABC abc = new ABC(); string str= "abc"; Console.WriteLine(Test(abc)); // Prints "Yes" Console.WriteLine(Test(str)); // Prints "No" } string Test<T>(ICollection<T> coll) {return "Yes";} string Test(object obj) {return "No";} }

  
  
  

• Janetjyothi

  Hi Mattias,

  I think you are definitely on the right track.

  Unfortunately GetGenericTypeDeclaration throws an exception indicating that the object is in an invalid state. I am not certain what "state" is required. Sadly I am trying to do this based on the type information, I do not have an instance. I feel that I might have been a little harsh to the first respondent. He might have been onto something there

  Another option may be to find instances of IEnumerable, but hard code ignoring the string class. I don't think any of the other primitive types support IEnumerable, so that might work in obtaining all the collections exposed by the class.

  Do you have any thoughts

  Regards

  Craig

  
  
• Determining if a generic Type implements ICollection