LINQ用于查询，而不用于更新数据.使用LINQ获取要修改的项目，然后在foreach循环中对其进行修改:

LINQ is for querying, not for updating the data. Use LINQ to get the items that you want to modify, and then modify them in a foreach loop:

foreach ( var tom in myList.Where(w => w.Name == "Tom")) {
    tom.Marks = 35;
}

演示.