Just want to make simple extension for syntactic sygar :
public static bool IsNotEmpty(this ICollection obj)
{
return ((obj != null)
&& (obj.Count > 0));
}
public static bool IsNotEmpty<T>(this ICollection<T> obj)
{
return ((obj != null)
&& (obj.Count > 0));
}
It works perfectly when I work with some collections, but when working with others I get
The call is ambiguous between the
following methods or properties:
'PowerOn.ExtensionsBasic.IsNotEmpty(System.Collections.IList)'
and
'PowerOn.ExtensionsBasic.IsNotEmpty(System.Collections.Generic.ICollection)'
Is there any canonical solution to this problem ?
No, I don't want to perform a cast before calling this method ;)
It's because some collections implements both interfaces, You should convert collection to concrete interface like this
((ICollection)myList).IsNotEmpty();
Or
((ICollection<int>)myIntList).IsNotEmpty();
And yea, you will get NullReferanceException if obj == null so you can remove null check ;) which mean that your extension method just compares Count whith 0 which you can do without extension method ;)
My best way to solve the ambiguity : define an overload for all common non-generic ICollection classes.
That means custom ICollection won't be compatible, but it's no big deal as generics are becoming the norme.
Here is the whole code :
/// <summary>
/// Check the given array is empty or not
/// </summary>
public static bool IsNotEmpty(this Array obj)
{
return ((obj != null)
&& (obj.Length > 0));
}
/// <summary>
/// Check the given ArrayList is empty or not
/// </summary>
public static bool IsNotEmpty(this ArrayList obj)
{
return ((obj != null)
&& (obj.Count > 0));
}
/// <summary>
/// Check the given BitArray is empty or not
/// </summary>
public static bool IsNotEmpty(this BitArray obj)
{
return ((obj != null)
&& (obj.Count > 0));
}
/// <summary>
/// Check the given CollectionBase is empty or not
/// </summary>
public static bool IsNotEmpty(this CollectionBase obj)
{
return ((obj != null)
&& (obj.Count > 0));
}
/// <summary>
/// Check the given DictionaryBase is empty or not
/// </summary>
public static bool IsNotEmpty(this DictionaryBase obj)
{
return ((obj != null)
&& (obj.Count > 0));
}
/// <summary>
/// Check the given Hashtable is empty or not
/// </summary>
public static bool IsNotEmpty(this Hashtable obj)
{
return ((obj != null)
&& (obj.Count > 0));
}
/// <summary>
/// Check the given Queue is empty or not
/// </summary>
public static bool IsNotEmpty(this Queue obj)
{
return ((obj != null)
&& (obj.Count > 0));
}
/// <summary>
/// Check the given ReadOnlyCollectionBase is empty or not
/// </summary>
public static bool IsNotEmpty(this ReadOnlyCollectionBase obj)
{
return ((obj != null)
&& (obj.Count > 0));
}
/// <summary>
/// Check the given SortedList is empty or not
/// </summary>
public static bool IsNotEmpty(this SortedList obj)
{
return ((obj != null)
&& (obj.Count > 0));
}
/// <summary>
/// Check the given Stack is empty or not
/// </summary>
public static bool IsNotEmpty(this Stack obj)
{
return ((obj != null)
&& (obj.Count > 0));
}
/// <summary>
/// Check the given generic is empty or not
/// </summary>
public static bool IsNotEmpty<T>(this ICollection<T> obj)
{
return ((obj != null)
&& (obj.Count > 0));
}
Note that I did not want it to work on IEnumerable<T>
, because Count()
is a method that can trigger a database request if you are working with Linq-to-Entity or Linq-to-SQL.