即使键属性存在，也没有键定义的错误

Question

我正在制作一个非常简单的MVC应用程序来管理一些家居事物。之前，我总是在MVC模型生成器（GUI事物）中创建我的数据模型，或者导入已经创建的SQL表。

这次，我想用代码优先的方法做到这一点。

我现向你的实体的例子：

public class Expense { 

    [Key] 
    public int ExpenseId; 

    public double ExpenseValue; 
    public DateTime ExpenseDate; 
    public string ExpenseDescription; 

    public ExpenseType ExpenseType; 
    public Currency ExpenseCurrency; 

    public List<ExpenseUser> Users; 

} 

而且我的DbContext派生类对象：

public class HawsContext : DbContext { 

    public DbSet<Expense> Expenses { get; set; } 
    public DbSet<ExpenseType> ExpenseTypes { get; set; } 
    public DbSet<ExpenseUser> ExpenseUsers { get; set; } 

    public ExpenseUser GetUserByUserName(string userName) { 
     return ExpenseUsers.Where(u => u.UserName == userName).FirstOrDefault(); 
    } 

} 

任何时候，我实例收到以下错误的对象：

One or more validation errors were detected during model generation:

\tSystem.Data.Entity.Edm.EdmEntityType: : EntityType 'Expense' has no key defined. Define the key for this EntityType. \tSystem.Data.Entity.Edm.EdmEntityType: : EntityType 'ExpenseType' has no key defined. Define the key for this EntityType. \tSystem.Data.Entity.Edm.EdmEntityType: : EntityType 'ExpenseUser' has no key defined. Define the key for this EntityType. \tSystem.Data.Entity.Edm.EdmEntitySet: EntityType: EntitySet 'Expenses' is based on type 'Expense' that has no keys defined. \tSystem.Data.Entity.Edm.EdmEntitySet: EntityType: EntitySet 'ExpenseTypes' is based on type 'ExpenseType' that has no keys defined. \tSystem.Data.Entity.Edm.EdmEntitySet: EntityType: EntitySet 'ExpenseUsers' is based on type 'ExpenseUser' that has no keys defined.

我在做什么错？我的所有实体都在其各自的键前面有[Key]，所有内容都可以在没有错误或警告的情况下编译。它只有在我实例化上下文时才起作用，大概是在它即将创建时（它实际上还没有创建任何SQL表）。

Answer 1

我在谷歌搜索中发现了这个问题。你必须让你的关键属性。