Linq to Entity 动态拼接查询条件(重点是OR)

1. public static class PredicateExtensions
   {
   /// <summary>
   /// 机关函数应用True时：单个AND有效，多个AND有效；单个OR无效，多个OR无效；混应时写在AND后的OR有效。即，设置为True时所有or语句应该放在and语句之后，否则无效
   /// </summary>
   public static Expression<Func<T, bool>> True<T>() { return f => true; }

   /// <summary>
   /// 机关函数应用False时：单个AND无效，多个AND无效；单个OR有效，多个OR有效；混应时写在OR后面的AND有效。 即，设置为False时所有or语句应该放在and语句之前，否则无效
   /// </summary>
   public static Expression<Func<T, bool>> False<T>() { return f => false; }

   public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expression1,
   Expression<Func<T, bool>> expression2)
   {
   var invokedExpression = Expression.Invoke(expression2, expression1.Parameters
   .Cast<Expression>());

   return Expression.Lambda<Func<T, bool>>(Expression.Or(expression1.Body, invokedExpression),
   expression1.Parameters);
   }

   public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expression1,
   Expression<Func<T, bool>> expression2)
   {
   var invokedExpression = Expression.Invoke(expression2, expression1.Parameters
   .Cast<Expression>());

   return Expression.Lambda<Func<T, bool>>(Expression.And(expression1.Body,
   invokedExpression), expression1.Parameters);
   }
   }

2. /// <summary>
   /// 获取指定type异常预警
   /// </summary>
   /// <param name="typeArray">整数数组</param>
   /// <returns></returns>
   public List<p2p_log_error> GetNewError(int[] typeArray)
   {
   var predicate = PredicateExtensions.False<p2p_log_error>();//设置为False，所有and条件都应该放在or之后，如where (type=1 or type=14) and status==0
   foreach (var t in typeArray)
   {
   int type_temp= t;
   predicate = predicate.Or(p => p.type == type_temp);
   }
   var result = entities.p2p_log_error.Where(predicate.Compile());
   return result.Where(p => p.status == 0).OrderByDescending(i => i.id).ToList();
   }