InvalidCastException：无法从源类型转换为目标类型。 （Unity C＃，foreach列表循环）

Question

嗨，我的代码有问题。

它抛出一个

  

InvalidCastException：无法从源类型转换为目标类型。

当尝试访问清单中的WeaponClass对象时：

public static List<ItemsClass> EquiptWeapon(EquipablesClass o, List<ItemsClass> inventory)

{//This function recive a item class (o) and a List


    if (o is WeaponsClass)
    {
        //This line here is the problematic one (InvalidCastException: Cannot cast from source type to destination type.)
        foreach (WeaponsClass z in inventory) {
           //This loop is made so if i already have a weapons equipped this will unequipped
           z.IsEquipted = false;
        }

       //Then i equip the weapon that was passed
        o.IsEquipted = true;

       //The player class has a weapon class in it, so now i assign it. So i can ask directly to the player class when i need the info
        WeaponsClass y = o as WeaponsClass;

        Player.player.WeaponEquip = y;

    }
    return inventory;
}

Answer 1

如果您确定List<ItemsClass> inventory中的每一项都是WeaponsClass类型，则可以执行以下操作：

foreach (var item in inventory.Cast<WeaponsClass>())
{
    //...
}

请注意，即使有一项无法转换为WeaponClass，也将引发异常。您可以采用的另一种方法是：

foreach (var item in inventory)
{
    var casted = item as WeaponClass; // No exception if cast fails, simply returns null
    if(casted != null)
    {
        //...
    }
}

您可以采用的另一种方法是：

foreach (var item in inventory.OfType<WeaponsClass>())
{
    //...
}

及其文档非常清楚：

  

根据指定的类型过滤System.Collections.IEnumerable的元素。