类型'System.String []'不支持比较运算符 [英] Comparison operators not supported for type 'System.String[]'
问题描述
为什么这行:
var category = _dataContext.Categories.Where<Category>(p => p.Keywords.Split(' ').Contains<string>(context.Request.QueryString["q"])).First();
抛出一个System.NotSupportedException:
throws an System.NotSupportedException:
类型'System.String []'不支持比较运算符
Comparison operators not supported for type 'System.String[]'
我该如何解决?
谢谢。
And how can I fix it? Thanks.
推荐答案
所以你正在寻找一个空格分隔的值(从查询字符串)列在数据库中?而您正在使用 Split
来查询数据库中的各个值?
So you are looking for a value (from the query-string) in a space-delimited column in the database? And you're using Split
to query the individual values inside the database?
(只是检查我的假设.. 。)
(just checking my assumptions...)
string.Split
不支持这种方式(列数据上的数据库) - 请参阅对于支持的字符串操作。 (请注意, string.Split
是显式不支持)
string.Split
is not supported in this way (at the database on column data) - see here for the supported string operations. (note that string.Split
is explicitly not supported).
我是懒;当我在数据库中划分数据(相对较少)时,我总是将相同的分隔符添加到数据的开始和结束;然后我可以搜索:
I'm lazy; when I delimit data in the database (relatively rare), I always add the same delimiter to the start and end of the data; then I can just search for:
string searchFor = DELIMITER + searchValue + DELIMITER;
...
.Where(row => row.Value.Contains(searchFor));
然而;在这种情况下,我期望最实用的选项可能是写一个UDF函数来搜索分隔的 varchar
(正确处理第一个/最后一个项目),并将UDF显示在数据上下文 - 然后使用:
However; in this case, I expect the most practical option might be to write a UDF function that searches a delimited varchar
(correctly handling the first/last item), and expose the UDF on the data-context - then use:
.Where(row => ctx.ContainsValue(row.Value, searchValue)); // ContainsValue is our UDF
或 - 规范化数据...
Or - normalise the data...
.Where(row => row.Values.Any(s=>s.Value == searchValue));
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