Question

• summary

  Ignore the case that an object cannot represented as an array, is it possible to define an extension(static) method like:

  public static ? ToArray<TSource>(this TSource source); 
  

  and returns the array of an object if it consists of whatever a sequence of elements? And if yes, what would the ? be?

• explanation

  I’ve thought about the following declarations:

  public static TElement[] ToArray<TElement>(this IEnumerable<TElement> source); 
  public static ? ToArray<TSource>(this IEnumerable source); 
  

  But I cannot assume an unknown class must have implemented IEnumerable<T> or IEnumerable. I cannot even define the ? in the case it is just IEnumerable which is out of generic definition.

  And I’ve also thought about the Array class:

  public static Array ToArray<TSource>(this TSource source); 
  

  But that means the element type was unknown at compile time.

  So I’m wondering is it possible to know the element type at compile time without a class implementing IEnumerable<T>?

Answer 1

Unfortunately, IEnumerator predates generics so it carries with it no type information; just a IEnumerator GetEnumerator() making String not so appealing to try and force into this generic implementation you’re trying to accomplish.

It’s been a long time since I’ve done C# but I imagine:

public static TElement ToArray<TSource>(this IEnumerable<TElement> source);

… should be fine as:

public static TElement[] ToArray<TElement>(this IEnumerable<TElement> source);

The important thing to keep in mind about extension methods is they are just syntax sugar. They don’t actually stick around or become injected into the types they are decorating. They are replaced at compile time to static method invocations. Your mileage with extension methods will vary.