这样做在LINQ字符串比较的问题 | 这样做在LINQ字符串比较的问题

本文介绍了这样做在LINQ字符串比较的问题的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我遇到了麻烦LINQ翻译一些东西到我需要的查询。在T-SQL中，我们做了＆LT; =和三列是CHAR（6）列> =比较。 LINQ不会允许，因为我做这件事

我有下面的T-SQL查询。

  SELECT *
FROM [ZIPMASTER] ZM
WHERE zm.CORP = 12
和'85546'zm.ZIPBEG和zm.ZIPEND间

以上是不是很LINQ freindly，由于没有用于不支持在。因此，我已经简化为以下内容：

  SELECT *
FROM [ZIPMASTER] ZM
WHERE zm.CORP = 12
与zm.ZIPBEG＆LT; ='85546'
与zm.ZIPEND＆GT; ='85546'

这是我用来创建以下LINQ查询：

  VAR zipLinqQuery =
    从ž在db.ZIPMASTERs
    其中，z.CORP == 12
    ＆功放;＆安培; z.ZIPBEG＆LT; =85546
    ＆功放;＆安培; z.ZIPEND＆GT; =85546
    特定的z;
名单＆LT; ZIPMASTER＆GT;拉链= zipLinqQuery.ToList＆LT; ZIPMASTER＆GT;（）;

C＃ - LINQ是不是喜欢这个查询太多。我想转换为整数，然后比较，但是，在某些情况下，压缩code可能包含一个字母。例如，下面的EX pression想要得到真正的T-SQL：

 其中85546B之间85546A和85546D

我不知道为什么它的作品在T-SQL，但我的猜测是，它在数组中通过将其转换为数字ASCII值进行比较，一个个字符分别。

总之，任何帮助，您都可以提供大大AP preciated。先谢谢了。

CJAM

解决方案（发表乔恩飞碟双向）：

看来，string.CompareTo（）事实上确实生成所需的T-SQL。下面的例子：

  VAR zipLinqQuery =
    从ž在db.ZIPMASTERs
    其中，z.CORP == listItem.CORP
    ＆功放;＆安培; z.ZIPBEG.CompareTo（listItem.ZIP code）＆LT; = 0
    ＆功放;＆安培; z.ZIPEND.CompareTo（listItem.ZIP code）＆GT; = 0
    特定的z;

生成以下的T-SQL：

  DECLARE @ P0 INT，@ P1 CHAR（6），@ p2的CHAR（6）
SET @ P0 = 12
SET @ P1 ='85546'
SET @ P2 ='85546'

选择[T0]。[CORP]，[T0]。[ZIPEND]，[T0]。[ZIPBEG]，[T0] [市]，[T0]。[状态]，[T0]。[CYCLE]
FROM [DBO]。[ZIPMASTER] AS [T0]
WHERE（[T0] [CORP] = @ P0）与（[T0] [ZIPBEG]其中; = @ P1）和（[T0] [ZIPEND]≥。= @ p2的）

解决方案

尝试：

  VAR zipLinqQuery =
    从ž在db.ZIPMASTERs
    其中，z.CORP == 12
    ＆功放;＆安培; z.ZIPBEG.CompareTo（85546）＆LT; = 0
    ＆功放;＆安培; z.ZIPEND.CompareTo（85546）＆GT; = 0
    特定的z;

我不的知道的是String.CompareTo工作在LINQ到SQL，但它的尝试的第一件事。

（通常情况下，你应该使用一个StringComparer指定正确类型的比较，但我怀疑在这种情况下的CompareTo是更好的选择。）

I'm having trouble getting LINQ to translate something into the query I need. In T-SQL, we do a <= and >= comparison on three columns that are CHAR(6) columns. LINQ will not allow me to do this since

I have the following T-SQL query..

SELECT *
FROM [ZIPMASTER] zm
WHERE zm.CORP = 12
AND '85546 ' BETWEEN zm.ZIPBEG AND zm.ZIPEND

The above is not very LINQ freindly, since there is no support for BETWEEN. Thus, I have simplified to the following:

SELECT *
FROM [ZIPMASTER] zm
WHERE zm.CORP = 12
AND zm.ZIPBEG <= '85546 '
AND zm.ZIPEND >= '85546 '

Which I have used to create the following LINQ query:

var zipLinqQuery =
    from z in db.ZIPMASTERs
    where z.CORP == 12
    && z.ZIPBEG <= "85546 "
    && z.ZIPEND >= "85546 "
    select z;
List<ZIPMASTER> zips = zipLinqQuery.ToList<ZIPMASTER>();

C# - LINQ is not liking this query too much. I tried converting to ints and then comparing, however, in some cases the zip code might contain a letter. For example, the following expression would evaluate to true in T-SQL:

WHERE '85546B' BETWEEN '85546A' AND '85546D'

I don't know exactly why it works in T-SQL, but my guess is that it compares each character in the array individually by converting it to a numerical ASCII value.

Anyway, any help you all can provide is greatly appreciated. Thanks in advance.

CJAM

Solution (posted by Jon Skeet):

It appears that string.CompareTo() does in fact generate the needed T-SQL. Examples below:

var zipLinqQuery =
    from z in db.ZIPMASTERs
    where z.CORP == listItem.CORP
    && z.ZIPBEG.CompareTo(listItem.ZIPCODE) <= 0
    && z.ZIPEND.CompareTo(listItem.ZIPCODE) >= 0
    select z;

Generates the following T-SQL:

DECLARE @p0 INT, @p1 CHAR(6), @p2 CHAR(6)
SET @p0 = 12
SET @p1 = '85546 '
SET @p2 = '85546 '

SELECT [t0].[CORP], [t0].[ZIPEND], [t0].[ZIPBEG], [t0].[CITY], [t0].[STATE], [t0].[CYCLE]
FROM [dbo].[ZIPMASTER] AS [t0]
WHERE ([t0].[CORP] = @p0) AND ([t0].[ZIPBEG] <= @p1) AND ([t0].[ZIPEND] >= @p2)

解决方案

Try:

var zipLinqQuery =
    from z in db.ZIPMASTERs
    where z.CORP == 12
    && z.ZIPBEG.CompareTo("85546 ") <= 0
    && z.ZIPEND.CompareTo("85546 ") >= 0
    select z;

I don't know that String.CompareTo works in LINQ to SQL, but it's the first thing to try.

(Normally you should use a StringComparer to specify the right type of comparison, but I suspect in this case CompareTo is the better option.)

这篇关于这样做在LINQ字符串比较的问题的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！