views:

384

answers:

2

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 ;)

+3  A: 

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 ;)

ArsenMkrt
*All* of the generic versions implement their non-generic counterparts, so any generic class would have both.
Rex M
yea, and may be he get this error on generic versions
ArsenMkrt
Like I said in the last sentence of my question, I don't want to perform a cast before the call.This is for SYNTACTIC SUGAR, if I need to add a cast, then it's definitely useless :pMy question remains : any way to solve ambiguity to work on all collections ?
Mose
@ArsenMkrt: extension methods can be called on variables with `value == null`, exception will not occur
Roman Boiko
@Rex M: did you mean all generic classes from .NET Framework implement non-generic interfaces? Is there any link to documentation?
Roman Boiko
+2  A: 

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.

Mose
After a few weeks using it, it is DEFINITELY the best solution, we mass-adopted it here.
Mose