Question

我是Entity Framework的新手。我从数据库第一种方法开始，创建了与我选择的表对应的类。我正在使用MVC。我的一个表格中有一个Date列。我的要求是我想在我的gridview（网格MVC）中显示日，即如果获取的特定记录的日期是10/27/2015，则日应该显示周二。我想这样做，而不是在我的数据库中添加额外的列。有没有办法解决这个问题。任何帮助将不胜感激。

我生成的模型类如下： -

public partial class QnsNew1
    {
        public int Id { get; set; }
        public Nullable<System.DateTime> Date { get; set; }
        public Nullable<int> PersonelID { get; set; }
        public string CType { get; set; }
        public string Comments { get; set; }
        //public string Day { get; set; }//I want to avoid doing this
        public virtual Personnel Personnel { get; set; }
        public virtual Type Type { get; set; }
    }

Answer 1

更好的方法

尽管可以使用Entity Framework轻松完成，但正如其他答案所指出的那样，并且我100％承认，通过创建与常规实体分开的ViewModel，最好将表示/ UI模型与数据库模型分开。把你的计算属性放在那里。

如果您遇到EF，请继续阅读

在EntityFramework Database First模式中，为数据库模型生成的类是分部类。您基本上可以创建另一个具有相同名称的部分类，并在相同的程序集和命名空间中，并在那里添加您的计算属性。

这是一个完整的例子（从这里的答案中借用一周的实施日期）：

public partial class MyTable
{
    [NotMapped]
    public string DayOfWeek
    { 
        get 
        { 
            if (Date.HasValue)
                return DateTime.Now.DayOfWeek.ToString();
            else
                return null;
        } 
    }
}

确保命名空间与生成的类相同非常重要。此外，您必须使用NotMapped属性注释该属性，以便EF不会尝试将该属性映射或保存回数据库。

Answer 2

使用相同的名称创建一个部分类，并具有一个名为Day的getter属性。这不会向您的数据库添加列。

public partial class QnsNew1
{
    public string Day
    {
        get
        {
            if (Date.HasValue)
                return DateTime.Now.DayOfWeek.ToString();
            else
                return null;
        }
    }
}

Answer 3

您可以在生成的数据/模型旁边添加passwords = ['mrjoebblock' , 'mrjoefblock' , 'mrjoegblock', 'mrjoeadmin' ] if choice == '3': password = raw_input('Welcome admin! I\'m going to need your password ') if password == 'mrjoeadmin': print('Welcome Mr. Joe!') Choice11 = raw_input('What would you like to do? Press 1 for changing your admin password, 2 for viewing a class\'s comments, or 3 for changing a class\'s password') if Choice11 == '1': print('You have chosen to change your password! ') Choice12 = raw_input('You will need to put in your current password to access this feature ') if Choice12 == 'mrjoeadmin': Choice13 = raw_input('What would you like to change your password to? ') passwords.remove('mrjoeadmin') passwords.append(Choice13) print('Thank you! Password has been changed. Log in with new password next time') break if Choice11 == '2': print('you have chosen to view a class\'s comments!') Choice14 = raw_input('Which block would you like to view?') if Choice14 == 'F block': print('To view F block\'s comments, go to where you search for things in your computer, and search CommentsFblock.txt. Open it') time.sleep(10) break if Choice14 == 'G block': print('To view G block\'s comments, go to where you search for things in your computer, and search CommentsGblock.txt. Open it') time.sleep(10) break if Choice14 == 'B block': print('To view B block\'s comments, go to where you search for things in your computer, and search CommentsBblock.txt. Open it') time.sleep(10) break else: print('I\'m sorry, that\'s not a valid block name.') time.sleep(2) break if Choice11 == '3': print('you have chosen to change a block\'s password.') Choice15 = raw_input('Which block\'s password would you like to change?') if Choice15 == 'F block': Choice16 = raw_input('You will need to put in your current password to change F block\'s password ') if Choice16 == 'mrjoeadmin': Choice17 = raw_input('What would you like to change F block\'s password to? ') passwords.remove('mrjoefblock') passwords.append(Choice17) print('Thank you! Password has been changed. Remember to tell students the password has been changed') time.sleep(3) break if Choice15 == 'G block': Choice18 = raw_input('You will need to put in your current password to change G block\'s password ') if Choice18 == 'mrjoeadmin': Choice19 = raw_input('What would you like to change G block\'s password to? ') passwords.remove('mrjoegblock') passwords.append(Choice19) print('Thank you! Password has been changed. Remember to tell students the password has been changed') time.sleep(3) break if Choice15 == 'B block': Choice20 = raw_input('You will need to put in your current password to change B block\'s password ') if Choice20 == 'mrjoeadmin': Choice21 = raw_input('What would you like to change B block\'s password to? ') passwords.remove('mrjoebblock') passwords.append(Choice21) print('Thank you! Password has been changed. Remember to tell students the password has been changed') time.sleep(3) break。但我可能会建议您将DataModel与演示模型分开，这是一个很好的理由。您的演示模型将包含仅用于演示的部分，并且是即时计算的，而您的数据模型应该严格代表您持久保存的数据。

Answer 4

考虑使用视图模型而不是实体框架创建的模型。由于您遇到的问题，我不喜欢在我的视图中使用数据库模型。相反，我创建了一个视图模型，然后使用AutoMapper或类似的库将数据从数据库模型复制到视图模型。

如何在不更改数据库模型的情况下在Entity Framework中添加新的实体属性

4 个答案:

更好的方法

如果您遇到EF，请继续阅读