i["ProjectLastUpdate"] 的值已经是一个 DateTime>，因此无需将其转换为字符串然后再解析回来.所以你可以使用一个简单的类型转换:

The value of i["ProjectLastUpdate"] already is a DateTime, so there's no need to convert it to a string and then parse it back. So you can use a simple typecast:

var mydate = (DateTime) i["ProjectLastUpdate"].