C＃ - 在SQL Server中更新DateTime列

this is my first post on the forum. I can't find any posts that answers my problem. If you do find one, please reply the link so I can take a look at it.

这是我在论坛上的第一篇文章。我找不到任何能解决我问题的帖子。如果你找到了，请回复链接，我可以看一下。

I am trying to update a DateTime column in SQL Server using C#.

我试图使用C＃更新SQL Server中的DateTime列。

In the first console application, I have already created an object:

在第一个控制台应用程序中，我已经创建了一个对象：

    NewCollegeEntities context = new NewCollegeEntities();

    College college = new College();
    college.collegeName = "BCIT";
    college.established = new DateTime(1960, 1, 1);

    context.Colleges.Add(college);
    context.SaveChanges();

Now, in the second console application, I am trying to add a day to the objected just created:

现在，在第二个控制台应用程序中，我正在尝试向刚刚创建的对象添加一天：

    NewCollegeEntities context = new NewCollegeEntities();

    College college = (from c in context.Colleges
                       where c.collegeName == "BCIT"
                       select c).FirstOrDefault();


    college.established.Value.AddDays(1);
    context.SaveChanges();

When I run the second console application, the results are the same as first console application-1960, 1, 1. It seems like I am not committing any changes to the database.

当我运行第二个控制台应用程序时，结果与第一个控制台应用程序-1960,1,1相同。看起来我没有对数据库进行任何更改。

Please help me understand what's going on and how to go about fixing this. Also let me know if you require more information! Thanks!

请帮助我了解正在发生的事情以及如何解决这个问题。如果您需要更多信息，请告诉我们！谢谢！

1 个解决方案

#1

This is a common oversight. The AddDays() method (and other similar methods) doesn't actually modify the value on which you invoke it. It returns a new DateTime which has the modified value.

这是一种常见的疏忽。 AddDays（）方法（以及其他类似方法）实际上并不会修改您调用它的值。它返回一个具有修改值的新DateTime。

Simply use that new DateTime:

只需使用新的DateTime：

college.established = college.established.Value.AddDays(1);

#1