方向

属性可以指向四个方向：

In：最常见。用于输入参数。
输出：用于输出参数，即活动的结果。
“输入输出”：很少使用，但在接收数据、修改数据并输出数据以供其他活动使用的活动中非常方便。
“无”：布尔值和枚举等独立类型不需要方向。创建这些类型的属性时，请使用“无”。

注意：在 UiPath Studio 中，Out 和 InOut 属性只能接受变量，而不能接受文本值。这是有道理的，因为活动需要可写入输出值的内容。

生成的代码

The Argument direction is seen in the declaration of each property. Notice that FirstNumber and SecondNumber are both InArguments while Sum is an OutArgument.

...
#region Properties
[LocalizedDisplayName(nameof(Resources.Addition_FirstNumber_DisplayName))]
[LocalizedDescription(nameof(Resources.Addition_FirstNumber_Description))]
[LocalizedCategory(nameof(Resources.Input_Category))]
public InArgument<int> FirstNumber { get; set; }
[LocalizedDisplayName(nameof(Resources.Addition_SecondNumber_DisplayName))]
[LocalizedDescription(nameof(Resources.Addition_SecondNumber_Description))]
[LocalizedCategory(nameof(Resources.Input_Category))]
public InArgument<int> SecondNumber { get; set; }
[LocalizedDisplayName(nameof(Resources.Addition_Sum_DisplayName))]
[LocalizedDescription(nameof(Resources.Addition_Sum_Description))]
[LocalizedCategory(nameof(Resources.Output_Category))]
public OutArgument<int> Sum { get; set; }
#endregion
......
#region Properties
[LocalizedDisplayName(nameof(Resources.Addition_FirstNumber_DisplayName))]
[LocalizedDescription(nameof(Resources.Addition_FirstNumber_Description))]
[LocalizedCategory(nameof(Resources.Input_Category))]
public InArgument<int> FirstNumber { get; set; }
[LocalizedDisplayName(nameof(Resources.Addition_SecondNumber_DisplayName))]
[LocalizedDescription(nameof(Resources.Addition_SecondNumber_Description))]
[LocalizedCategory(nameof(Resources.Input_Category))]
public InArgument<int> SecondNumber { get; set; }
[LocalizedDisplayName(nameof(Resources.Addition_Sum_DisplayName))]
[LocalizedDescription(nameof(Resources.Addition_Sum_Description))]
[LocalizedCategory(nameof(Resources.Output_Category))]
public OutArgument<int> Sum { get; set; }
#endregion
...