如何在EF CodeFirst中使用唯一约束（Unique）

一直用EF Fluent Api 做MapConfiguration

所以遇到了唯一约束这个瓶颈

 

使用唯一约束的两种方式：

 

方式1 自定义唯一约束

 

[AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)]

public class UniqueAttribute : ValidationAttribute

{

   public override Boolean IsValid(Object value)

    {

        //校验数据库是否存在当前Key

        return true;

    }

}

View Code

 

在Model类中使用

public class Email

    {

    [Key]

    public int EmailID { get; set; }



    public int PersonId { get; set; }



    [Unique]

    [Required]

    [MaxLength(100)]

    public string EmailAddress { get; set; }

    public virtual bool IsDefault { get; set; }

    public virtual Boolean IsApprovedForLogin { get; set; }

    public virtual String ConfirmationToken { get; set; }



    [ForeignKey("PersonId")]

    public virtual Person Person { get; set; }

}

View Code

 

方式2 扩展DataBaseSetInitializer 使用Sql语句添加

public class MyInitializer : CreateDatabaseIfNotExists<MyContext>

{

  protected override void Seed(MyContext context)

  {

    context.Database.ExecuteSqlCommand("CREATE UNIQUE INDEX IX_Category_Title ON Categories (Title)");

  }

}

View Code

 

在DbContext中使用

Database.SetInitializer<MyContext>(new MyInitializer());

View Code

 

方式3 扩展IDatabaseInitializer

public class Initializer : IDatabaseInitializer<myEntities>

        {

            public void InitializeDatabase(myEntities context)

            {

                if (System.Diagnostics.Debugger.IsAttached && context.Database.Exists() && !context.Database.CompatibleWithModel(false))

                {

                    context.Database.Delete();

                }



                if (!context.Database.Exists())

                {

                    context.Database.Create();



                    var contextObject = context as System.Object;

                    var contextType = contextObject.GetType();

                    var properties = contextType.GetProperties();

                    System.Type t = null;

                    string tableName = null;

                    string fieldName = null;

                    foreach (var pi in properties)

                    {

                        if (pi.PropertyType.IsGenericType && pi.PropertyType.Name.Contains("DbSet"))

                        {

                            t = pi.PropertyType.GetGenericArguments()[0];



                            var mytableName = t.GetCustomAttributes(typeof(TableAttribute), true);

                            if (mytableName.Length > 0)

                            {

                                TableAttribute mytable = mytableName[0] as TableAttribute;

                                tableName = mytable.Name;

                            }

                            else

                            {

                                tableName = pi.Name;

                            }



                            foreach (var piEntity in t.GetProperties())

                            {

                                if (piEntity.GetCustomAttributes(typeof(UniqueAttribute), true).Length > 0)

                                {

                                    fieldName = piEntity.Name;

                                    context.Database.ExecuteSqlCommand("ALTER TABLE " + tableName + " ADD CONSTRAINT con_Unique_" + tableName + "_" + fieldName + " UNIQUE (" + fieldName + ")");

                                }

                            }

                        }

                    }

                }

            }

        }

View Code

在DbContext中使用

System.Data.Entity.Database.SetInitializer<MyApp.Models.DomainModels.myEntities>(new MyApp.Models.DomainModels.myEntities.Initializer());

View Code

 

参考文献：http://stackoverflow.com/questions/5701608/unique-key-with-ef-code-first