Determine if an object is an array of any type, and access the array length

Question

I have an overridden method that has an object parameter. I am determining if this is an array, and then want to determine its length:

public override bool IsValid(object value)
{
    Type type = value.GetType();
    if (type.IsArray)
    {
        return ((object[]) value).Length > 0;
    }
    else
    {
        return false;
    }
}

The problem is if value is an int[], it errors when I try to cast to an object[]. Is there any way to handle this cast so it will work with any type of array?

Answer 1

Cast value to the base System.Array class:

return ((Array) value).Length > 0

By using the as operator, you can simplify your code further:

public static bool IsValid(object value)
{
    Array array = value as Array;
    return array != null && array.Length > 0;
}

Note: This will return true for multidimensional arrays such as new int[10, 10]. If you want to return false in this case, add a check for array.Rank == 1.

Answer 2

An alternative approach that avoids having to interrogate the type in your validation method is to use dynamic dispatch:

// Default overload
public static bool IsValid(object value) 
{ return false; }

// If it's an array
public static bool IsValid(Array value)
{
    return value.Length > 0;
}

...

bool isValid = IsValid((dynamic)obj); // Will call the overload corresponding to type of obj