类型“System.String[]"不支持比较运算符

问题描述

为什么是这条线:

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.

推荐答案

所以您正在数据库中以空格分隔的列中寻找值(来自查询字符串)?并且您正在使用 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(在列数据的数据库中) - 请参阅此处了解 支持的字符串操作.(注意 string.Split 显式不被支持).

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).

我很懒；当我在数据库中对数据进行分隔时(比较少见)，我总是在数据的开头和结尾添加相同的分隔符；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，我希望最实用的选择可能是编写一个 UDF 函数来搜索分隔的 varchar(正确处理第一个/最后一个项目)，并在数据上下文中公开 UDF - 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

或者 - 标准化数据...

Or - normalise the data...

.Where(row => row.Values.Any(s=>s.Value == searchValue));