ArrayList 存储System.Object 的列表.您需要将对象强制转换回 DataPerLabel，如下所示:

ArrayList stores a list of System.Object. You need to cast the object back to DataPerLabel as follows:

foreach (var item in allData)
{
    ((DataPerLabel)item).getLabelName();
}

或者，您可以在 foreach 中指定数据类型而不是 var 作为 Jakub Dąbek 在评论中指出:

Alternatively, you could specify the data type in the foreach instead of var as Jakub Dąbek pointed out in the comment as follows:

foreach (DataPerLabel item in allData)
{
    item.getLabelName();
}

更好的方法是使用通用列表/集合 List 来存储数据，从而避免强制转换.

A better approach would be to use generic list/collection List<DataPerLabel> to store the data so that the casting can be avoided.