C#检查指定对象是否存在于ArrayList集合中的方法

ArrayList alcollect = new ArrayList();
// Add individual items to the collection
string str = "learn csharp";
alcollect.Add(str);
//check existence of object
if(alcollect.Contains(str))
{
  Console.WriteLine(alcollect.IndexOf(str));
}
else
{
  Console.WriteLine("Not found!");
}