Question

如何在选中的 sql 查询后写入 LINQ 查询 :

string brandid="1,2,3"
string bodystyleid="1,2,3"
-------------------
-----------------

select * from car
where brandid in (brandid)
and bodystyleid in (brandid)
----------------------
-------------------

My specific requirement is that if brandid or bodystyleid is blank(if user does not select any checkbox of a particular search option) query should return all record for that particular where condition.

请指引我

谢谢

保罗保罗

Answer 1

如果您没有指定要返回的所有项目,为了满足要返回所有项目的要求,您需要检查列表是否为空。

var brands = brandid.Split( , ).Select(x => Int32.Parse(x));
var styles = bodystyleid.Split( , ).Select(x => Int32.Parse(x));

var result = from c in car
             where (!brands.Any() || brands.Contains(c.brandid))
                  && (!styles.Any() || styles.Contains(c.bodystyleid))
             select c;

(类似于 sgmoore s 溶液, 但包括未指定品牌/ 风格的检查)

我还没有实际检查它是如何被转换回 SQL - 使用旗帜来显示是否有值可能更有效率 :

var brands = ....;   // As above
bool anyBrands = brands.Any()
var result = from c in car
             where (!anyBrands || brands.Contains(c.brandid))
               .....

Answer 2

体型是用来检查品牌还是体型? (我假定是体型,但写了查询来与问题中的查询吻合(brandid))

作为开始,你可以做:

var results = (from c in car
               where c.brandid.Contains(brandid)
               && c.bodystyleid.Contains(brandid)
               select c).ToList();

Answer 3

var brandids     = brandid    .Split( , ).Select(n => int.Parse(n)).ToList();
var bodyStyleids = bodystyleid.Split( , ).Select(n => int.Parse(n)).ToList();


var results =
    (from c in car where 
      brandids.Contains(c.brandid) && 
      bodyStyleids.Contains(c.bodystyleid) 
     select c
   ).ToList();

Answer 4

您拥有的 Id 作为逗号分隔符的字符串, 您需要它们像您 list 表格的 Car 表格的 > Id 一样, 像 list 一样的收藏, 所以, 如果 brandidd 列是 int 那么 > brandids 必须是 list< long> , 那么你可以这样做。



var results = (
    from c in cars
    where brandids.Contains(c.brandid) && bodystyleid.Contains(c.bodystyleid) 
    select c).ToList();

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