Question

This might be a stupid question, but is there any common practice for initializing collection properties for a user, so they don’t have to new up a new concrete collection before using it in a class?

Are any of these preferred over the other?

Option 1:

public class StringHolderNotInitialized {     // Force user to assign an object to MyStrings before using     public IList<string> MyStrings { get; set; } } 

Option 2:

public class StringHolderInitializedRightAway {     // Initialize a default concrete object at construction      private IList<string> myStrings = new List<string>();      public IList<string> MyStrings     {         get { return myStrings; }         set { myStrings = value; }     } } 

Option 3:

public class StringHolderLazyInitialized {     private IList<string> myStrings = null;      public IList<string> MyStrings     {         // If user hasn't set a collection, create one now         // (forces a null check each time, but doesn't create object if it's never used)         get         {             if (myStrings == null)             {                 myStrings = new List<string>();             }             return myStrings;         }         set         {             myStrings = value;         }     } } 

Option 4:

Any other good options for this?

Answer 1

In this case, I don’t see the reason for the lazy loading, so I would go with option 2. If you are creating a ton of these objects, then the number of allocations and GCs that result would be an issue, but that’s not something to consider really unless it proves to be a problem later.

Additionally, for things like this, I would typically not allow the assignment of the IList to the class. I would make this read-only. In not controlling the implementation of the IList, you open yourself up to unexpected implementations.