using System;using System.ComponentModel.DataAnnotations;using System.Data.Entity;namespace Zwj.TEMS.Base{    /// 
    /// 唯一性标识    /// 
    [AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)]    public class UniqueAttribute : ValidationAttribute    {        protected string tableName;        protected string filedName;        public UniqueAttribute(string tableName, string filedName)        {            this.tableName = tableName;            this.filedName = filedName;        }        public override Boolean IsValid(Object value)        {            bool validResult = false;            //TEMSContext 是我项目中的DB上下文类，若需要使用在其它项目中，请更改成实际的DB上下文类就可以了！            using (TEMSContext context = new TEMSContext())            {               string sqlCmd=string.Format("select count(1) from [{0}] where [{1}]=@p0",tableName,filedName);               context.Database.Connection.Open();               var cmd=context.Database.Connection.CreateCommand();               cmd.CommandText = sqlCmd;               var p0 = cmd.CreateParameter();               p0.ParameterName = "@p0";               p0.Value = value;               cmd.Parameters.Add(p0);               int result=Convert.ToInt32(cmd.ExecuteScalar());                validResult=(result<=0);            }            return validResult;        }    }}

在实体中使用方法如下：

/// 
        /// 类别代码        /// 
        [Required()]        [MaxLength(50)]        [Unique("Category", "CategoryCode")]        [Display(Name = "类别代码")]        public string CategoryCode { get; set; }

 

调用与验证方法如下：

//我这里写了一个单元测试的验证方法，大家可以用在实际项目中        public void ValidateEntity(object entity)        {            var t = entity.GetType();            var properties = t.GetProperties();            foreach (var p in properties)            {                UniqueAttribute[] attrs;                if (p.TryGetAttribute
    
     (out attrs))                {                    bool result = attrs[0].IsValid(p.GetValue(entity, null));                    Assert.IsTrue(result, "验证不唯一，存在重复值！");                }            }        }
    

public static class ClassExtension    {        /// 
        /// 尝试获取指定类别特性        /// 
        /// 
            ///         ///         /// 
            public static bool TryGetAttribute
    
     (this PropertyInfo p, out TAttribute[] returnAttrs) where TAttribute : Attribute        {            var attrs = p.GetCustomAttributes(typeof(TAttribute), false);            if (attrs != null && attrs.Length > 0)            {                returnAttrs = attrs.Select(t => t as TAttribute).ToArray();                return true;            }            returnAttrs=null;            return false;        }    }