大家一起来学习一下面向对象的三层架构吧!今天我来说说Entity有时也叫MODEL实体层!

实体层,事实上就是数据库的对象化,把数据表抽象化,目前有很多这方面的工具,我们把这些工具称为ORM工具,即对象关系模型,microsoft在进入3.5时代后引入了LINQ的概念,LINQ的出现,大大提高了开发人员工作效率,它把传统的数据库直接对象了,并以IQueryable<T>的形式被以提供访问，它被称为是可查询的结果集，我们也可以把它理解为是一个ＶＳ项目里的数据库．

不说费话了，还是看看我的实体设计吧！

  1:  #region 对实体层的实现

  2:      /// <summary>

  3:      /// 实体通用接口

  4:      /// </summary>

  5:      public interface IDataEntity

  6:      {

  7:      }

  8:      /// <summary>

  9:      /// 实体验证接口

 10:      /// </summary>

 11:      public interface IEntity

 12:      {

 13:          /// <summary>

 14:          /// 实体是否有效,只提供读方法,它直接返回本类某方法的类即可,所以不提供set

 15:          /// </summary>

 16:          bool IsValid { get; }

 17:          /// <summary>

 18:          /// 验证迭代器

 19:          /// </summary>

 20:          /// <returns></returns>

 21:          IEnumerable<RuleViolation> GetRuleViolations();

 22:      }

 23:      /// <summary>

 24:      /// 验证类结构

 25:      /// </summary>

 26:      public class RuleViolation

 27:      {

 28:          public string ErrorMessage { get; private set; }

 29:          public string PropertyName { get; private set; }

 30:          public RuleViolation(string propertyName, string errorMessage)

 31:          {

 32:              this.ErrorMessage = errorMessage;

 33:              this.PropertyName = propertyName;

 34:          }

 35:          public RuleViolation(string errorMessage)

 36:          {

 37:              this.ErrorMessage = errorMessage;

 38:          }

 39:      }

 40:      public partial class Department : IDataEntity

 41:      {

 42:          //初始字段

 43:          #region original field

 44:   

 45:          /// <summary>

 46:          /// 

 47:          /// </summary>

 48:          public int DeptID { get; set; }

 49:   

 50:          /// <summary>

 51:          /// 

 52:          /// </summary>

 53:          public string DeptName { get; set; }

 54:   

 55:          /// <summary>

 56:          /// 

 57:          /// </summary>

 58:          public DateTime CreateDate { get; set; }

 59:   

 60:          /// <summary>

 61:          /// 

 62:          /// </summary>

 63:          public DateTime UpdateDate { get; set; }

 64:   

 65:          /// <summary>

 66:          /// 

 67:          /// </summary>

 68:          public string Operator { get; set; }

 69:   

 70:          /// <summary>

 71:          /// 上一级ID，最高级别的父ID为0

 72:          /// </summary>

 73:          public int ParentID { get; set; }

 74:   

 75:          #endregion

 76:  

 77:          //外延字段

 78:          #region extensional field

 79:          #endregion

 80:  

 81:          //构造函数

 82:          #region constructed function

 83:   

 84:          /// <summary>

 85:          /// 新建立的时候构造函数

 86:          /// </summary>

 87:          public Department()

 88:          {

 89:   

 90:          }

 91:   

 92:          /// <summary>

 93:          /// 新建立的时候构造函数

 94:          /// </summary>

 95:          /// <param name="_DeptID"></param>

 96:          public Department(Int32 _DeptID)

 97:          {

 98:              this.DeptID = _DeptID;

 99:   

100:          }

101:   

102:          #endregion

103:  

104:          //方法

105:          #region function

106:   

107:          #endregion

108:  

109:          //重写方法

110:          #region object overrides

111:   

112:          #endregion

113:      }

114:   

115:      public partial class Department : IEntity

116:      {

117:   

118:          #region IEntity 成员

119:   

120:          public bool IsValid

121:          {

122:              get { return (GetRuleViolations().Count() == 0); }

123:          }

124:   

125:          public IEnumerable<RuleViolation> GetRuleViolations()

126:          {

127:              if (String.IsNullOrEmpty(this.DeptName))

128:                  yield return new RuleViolation("不能为空", "DeptName");

129:              if (String.IsNullOrEmpty(this.Operator))

130:                  yield return new RuleViolation("不能为空", "Operator");

131:              yield break;

132:          }

133:   

134:          #endregion

135:      }

136:   

137:      #endregion

看清楚了吧，我们的实体是由两部分组成了，即＂实体的基本属性＂和＂实体的验证机制＂哈哈

去感受吧！