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[ASP.net教程]实现UniqueAttribute唯一性约束


using System;using System.ComponentModel.DataAnnotations;using System.Data.Entity;namespace Zwj.TEMS.Base{  /// <summary>  /// 唯一性标识  /// </summary>  [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:

    /// <summary>    /// 类别代码    /// </summary>    [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<UniqueAttribute>(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  {    /// <summary>    /// 尝试获取指定类别特性    /// </summary>    /// <typeparam name="TAttribute"></typeparam>    /// <param name="p"></param>    /// <param name="returnAttrs"></param>    /// <returns></returns>    public static bool TryGetAttribute<TAttribute>(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;    }  }

 



以下是博客园的相关文章,他主要描述的是如何在数据库中生成唯 一性索引,而对如何在C#进行唯一性验证并没有说明,我这篇文章仅作一个补充。

如何在EF CodeFirst中使用唯一约束(Unique)