This website requires Javascript to function properly. Please go to the setting of your web browser and enable Javascript for this website.

Ad by

记得这里有几位LINQ大侠，来求助一下关于如何在LINQ里实现between。

mfcguy()

现在需要filter某个字段按照给定的范围，用SQL如下：
select ProductType from Products
where ProductType between 'A' and 'C'
order by ProductType
网上找到一个BetweenExtensions(http://www.hookedonlinq.com/BetweenOperator.ashx)，不能用，因为我需要的是N多个filters一起作用后的最终结果，
var query= from p in db.Products
joint xxx
select new { xxx, yyy, zzz ... }
if(...)
query=query.where(condition1);
if(...)
query=query.where(condition2);
if(...)
query=query.where(conditionN);

这样一层层把结果范围缩小，最后送给Gridview显示出来，所以返回结果必须是IQueryable类型，而BetweenExtension里的类型是IEnumerable，如果简单的把IEnumerable换成IQueryable，里面的iterator和IQueryable冲突。

(#4871602@0)
Last Updated: 2008-11-25
This post has been archived. It cannot be replied.

Report

Replies, comments and Discussions:

工作学习 / 学科技术讨论 / 记得这里有几位LINQ大侠，来求助一下关于如何在LINQ里实现between。 -mfcguy(); 2008-11-25 {744} (#4871602@0)
现在需要filter某个字段按照给定的范围，用SQL如下：
select ProductType from Products
where ProductType between 'A' and 'C'
order by ProductType
网上找到一个BetweenExtensions(http://www.hookedonlinq.com/BetweenOperator.ashx)，不能用，因为我需要的是N多个filters一起作用后的最终结果，
var query= from p in db.Products
joint xxx
select new { xxx, yyy, zzz ... }
if(...)
query=query.where(condition1);
if(...)
query=query.where(condition2);
if(...)
query=query.where(conditionN);

这样一层层把结果范围缩小，最后送给Gridview显示出来，所以返回结果必须是IQueryable类型，而BetweenExtension里的类型是IEnumerable，如果简单的把IEnumerable换成IQueryable，里面的iterator和IQueryable冲突。

How about using ProductType >= 'A' && ProductType <='C' -deep_blue(BLUE); 2008-11-26 (#4873091@0)

Operator '>=' cannot be applied to operands of type 'string' and 'char' -mfcguy(); 2008-11-26 (#4874172@0)

It’s just a prototype. Do I have to write out whole thing? -deep_blue(BLUE); 2008-11-26 {99} (#4874205@0)
query = query.where(p => p.ProductType.CompareTo(“A”) >=0 && p.ProductType.CompareTo(“C”) <=0);

Thanks a lot, it works perfect! -mfcguy(); 2008-11-26 (#4874373@0)

Actually you can directly use IEnumerable (base of IQueryable) as datasource of gridview. -deep_blue(BLUE); 2008-11-26 (#4873139@0)

Have you ever tried? -mfcguy(); 2008-11-26 {307} (#4874199@0)
if I define query like:
IEnumerable query= from a in db.Products
......
query.Where() query.Between() won't be seen
only I use 'var' instead of 'IEnumerable' can solve this problem, but type 'var' will be dynamically assign into 'IQueryable<>' in run time

Of course you cannot use IEnumerable. You have to use IEnumerable<T>. It means you shouldn’t use anonymous query result. As matter factor, if you use anonymous query result, you’ll also have trouble to pass query result to other layer. -deep_blue(BLUE); 2008-11-26 (#4874353@0)

you reached the point, I had gotten some problem last time when I tried to pass the value of result between objects due to using anonymous query result. Thanks for your words. -mfcguy(); 2008-11-26 (#4874385@0)

@Calgary

记得这里有几位LINQ大侠，来求助一下关于如何在LINQ里实现between。

Replies, comments and Discussions:

More Topics