直到目前为止，EntityFramework似乎没有UniqueAttribute这个属性，因而也就无法为数据模型表某个特定字段指定是Unique。那么怎么办呢？我们就DIY一次吧！

首先自己写一个特性，该特性只能被用于property上，由于只是一个标记特性而以，因此类体为空——

[C#]

[AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)]    public class UniqueKeyAttribute : Attribute    {    }

[VB.NET]

     
       _Public Class UniqueKeyAttribute    Inherits AttributeEnd Class
     

然后自己实现IDatabaseInitializer接口。那是因为EntityFramework的DataBase有一个静态方法叫做SetInitialize<T>，其中“T”是预备生成的模型类（继承DbContext），而这个方法需要一个实现该接口的类用于初始化数据库。该类实现如下：

[C#]

public class MyDbGenerator
     
       : IDatabaseInitializer
      
        where T : DbContext    {        public void InitializeDatabase(T context)        {               context.Database.Delete();                context.Database.Create();                //获取全部父类的公开属性
      
     

var fatherPropertyNames = typeof(DbContext).GetProperties().Select(pi => pi.Name).ToList();                //先剔除由父类继承的公共属性

foreach (PropertyInfo item in typeof(T).GetProperties().Where(p => fatherPropertyNames.IndexOf(p.Name) < 0).Select(p => p))                {                    //获取子类DbSet
     
      中的那个"T"
     

Type entityModelType = item.PropertyType.GetGenericArguments()[0];                    //反射“T”，并且获取已经加上“Unique”的自定义属性字段名称

var allfieldNames = from prop in entityModelType.GetProperties()                                        where prop.GetCustomAttributes(typeof(UniqueKeyAttribute), true).Count() > 0                                        select prop.Name;                    //逐个开始用SQL命令生成唯一字段

foreach (string s in allfieldNames)                    {                        context.Database.ExecuteSqlCommand("alter table " + entityModelType.Name + " add unique(" + s + ")");                    }                }                           }    }

[VB.NET]

Public Class MyDbGenerator(Of T As DbContext)    Implements IDatabaseInitializer(Of T)    Public Sub InitializeDatabase(context As T)        context.Database.Delete()        context.Database.Create()        '获取全部父类的公开属性                        Dim fatherPropertyNames = GetType(DbContext).GetProperties().[Select](Function(pi) pi.Name).ToList()        '先剔除由父类继承的公共属性                        For Each item As PropertyInfo In GetType(T).GetProperties().Where(Function(p) fatherPropertyNames.IndexOf(p.Name) < 0).[Select](Function(p) p)            '获取子类DbSet
     
      中的那个"T"                               Dim entityModelType As Type = item.PropertyType.GetGenericArguments()(0)            '反射“T”，并且获取已经加上“Unique”的自定义属性字段名称                                Dim allfieldNames = From prop In entityModelType.GetProperties() Where prop.GetCustomAttributes(GetType(UniqueKeyAttribute), True).Count() > 0prop.Name            '逐个开始用SQL命令生成唯一字段                                For Each s As String In allfieldNames                context.Database.ExecuteSqlCommand("alter table " + entityModelType.Name & " add unique(" & s & ")")            Next        Next    End SubEnd Class
     

下面给出测试：

[C#]

public class Category    {        [Key]        public int Id { get; set; }        [UniqueKey]        public int IdentifyCode { get; set; }        public string Name { get; set; }    }    public class DbG : DbContext    {        protected override void OnModelCreating(DbModelBuilder modelBuilder)        {            modelBuilder.Conventions.Remove
     
      ();        }        public DbSet
      
        Categories { get; set; }    }    public class MainTest    {        static void Main(string[] args)        {            Database.SetInitializer
       
        (new MyDbGenerator
        
         ());            using (DbG g = new DbG())            {                g.Categories.Add(new Category { Id = 1, Name = "Category" });                g.SaveChanges();                Console.WriteLine("OK");            }        }    }
        
       
      
     

[VB.NET]

copy to clipboard | view source | convert again Public Class Category    
     
       _    Public Property Id() As Integer        Get            Return m_Id        End Get        Set            m_Id = Value        End Set    End Property    Private m_Id As Integer    
      
        _    Public Property IdentifyCode() As Integer        Get            Return m_IdentifyCode        End Get        Set            m_IdentifyCode = Value        End Set    End Property    Private m_IdentifyCode As Integer    Public Property Name() As String        Get            Return m_Name        End Get        Set            m_Name = Value        End Set    End Property    Private m_Name As StringEnd ClassPublic Class DbG    Inherits DbContext    Protected Overrides Sub OnModelCreating(modelBuilder As DbModelBuilder)        modelBuilder.Conventions.Remove(Of PluralizingTableNameConvention)()    End Sub    Public Property Categories() As DbSet(Of Category)        Get            Return m_Categories        End Get        Set            m_Categories = Value        End Set    End Property    Private m_Categories As DbSet(Of Category)End ClassPublic Class MainTest    Private Shared Sub Main(args As String())        Database.SetInitializer(Of DbG)(New MyDbGenerator(Of DbG)())        Using g As New DbG()            g.Categories.Add(New Category() With { _                Key .Id = 1, _                Key .Name = "Category" _            })            g.SaveChanges()            Console.WriteLine("OK")        End Using    End SubEnd Class
      
     

注意：此处的“OnModelCreating”方法必须被重写。因为默认情况下Code-First生成的数据表名总是“实体模型名”（复数）形式，而我的代码目前只考虑了（直接根据模型名）生成表（也就是Add unique这部分）。因此必须取消表的“自动复数化”形式。除了我的这个方法以外，其实还可以采用在模型类上冠以“Table("表名称")”的形式。

测试代码是成功的，不过有时会出现表无法删除的情况，望大伙儿可以指教一二，谢谢！

如果有其它想法或者意见，也请及时反馈，谢谢！