学习并使用了两种linq to entity 的实现sql关键字in的查询方法

//构造Lambda语句
        private static Expression<Func<TElement, bool>> BuildWhereInExpression<TElement, TValue>(Expression<Func<TElement, TValue>> propertySelector, IEnumerable<TValue> values)
         {
             ParameterExpression p = propertySelector.Parameters.Single();
             if (!values.Any())
                 return e => false;
            var equals = values.Select(value => (Expression)Expression.Equal(propertySelector.Body, Expression.Constant(value, typeof(TValue))));
             var body = equals.Aggregate<Expression>((accumulate, equal) => Expression.Or(accumulate, equal));
            return Expression.Lambda<Func<TElement, bool>>(body, p);
         }
//调用
       string[] ids = new string[]{"id1","id2","id3"}；
       db.ProjectFiles.Where(BuildWhereInExpression<Profile,int>(v=>v.Id,ids);
//封装方法
        public static IQueryable<TElement> WhereIn<TElement, TValue>(this IQueryable<TElement> source, Expression<Func<TElement, TValue>> propertySelector, params TValue[] values)
         {
             return source.Where(BuildWhereInExpression(propertySelector, values));
         }
 //直接使用下列方法调用
      string[] ids = new string[]{"id1","id2","id3"}；
       db.ProjectFiles.WhereIn(c => c.Id,ids);
 //字符串构造
 //这个方法比较简单
      string[] ids = new string[]{"id1","id2","id3"}；
       cstIds=cstIds.Replace(",","','");
       var query = db.ProjectFiles.Where("it.Id in {'" + cstIds + "'}");