length of array

static void TestArray(Args _args)
{
    Array   strArray = new Array(Types::String);
    ;

    strArray.value(1, 'abc');
    strArray.value(2, 'def');

    info(strfmt("%1", strArray.lastIndex()));
}

for more info please have a look............

http://msdn.microsoft.com/en-us/library/array.aspx