Dapper是否支持like运算符？ [英] Does Dapper support the like operator?

问题描述

使用Dapper-dot-net ...

Using Dapper-dot-net...

以下在数据对象中不会产生任何结果：

The following yields no results in the data object:

var data = conn.Query(@"
    select top 25 
    Term as Label, 
    Type, 
    ID 
    from SearchTerms 
    WHERE Term like '%@T%'", 
    new { T = (string)term });

但是，当我只使用常规字符串格式，如：

However, when I just use a regular String Format like:

string QueryString = String.Format("select top 25 Term as Label, Type, ID from SearchTerms WHERE Term like '%{0}%'", term);
var data = conn.Query(QueryString);

我在集合中得到了25行。 Dapper是否无法正确解析参数 @T 的结尾？

I get 25 rows back in the collection. Is Dapper not correctly parsing the end of the parameter @T?

推荐答案

尝试：

term = "whateverterm";
var encodeForLike = term => term.Replace("[", "[[]").Replace("%", "[%]");

string term = "%" + encodeForLike(term) + "%";
var data = conn.Query(@"
   select top 25 
  Term as Label, 
  Type, 
  ID 
  from SearchTerms 
  WHERE Term like @term", 
  new { term });

类似运算符没有什么特别的，您永远不要将参数放在字符串文字中，它们将无法工作，而是将它们解释为字符串。

There is nothing special about like operators, you never want your params inside string literals, they will not work, instead they will be interpreted as a string.

注意

强烈建议您不要在第二个代码段中使用代码编码的示例，除了这是sql注入的巨大问题之外，它还可能导致dapper泄漏。

The hard-coded example in your second snippet is strongly discouraged, besides being a huge problem with sql injection, it can cause dapper to leak.

凹腔

任何喜欢以通配符开头的匹配项不可SARGable，这意味着它很慢，需要进行索引扫描。

Any like match that is leading with a wildcard is not SARGable, which means it is slow and will require an index scan.

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