SerializationException 无法捕捉（catch）

try
{if (CheckChanged()){CurrenExcuse = new Excuse(random, selectedFolder);UpdateForm(false);}

}
catch (SerializationException)
{MessageBox.Show("You excuse file was invalid.", "Unable to open a random excuse");
}

在处理异常的时候以上代码需要在最前面增加一句

using System.Runtime.Serialization;

可以在这个网页查询到相关信息：https://msdn.microsoft.com/en-us/library/system.runtime.serialization.serializationexception(v=vs.110).aspx