我的网站有一堆小部件,我正在尝试根据传入的网址过滤它们。假设一个小部件具有以下结构:
public class Widget {
public int Id { get; set; }
public string Name { get; set; }
public string Urls { get; set; }
}
其中Url是应显示小部件的网址的逗号分隔列表,例如:
/,/ Blog /,/ Blog / 123,/ News / *
新闻后的星号表示只要传入的网址以/ News /开头,就会选择小工具。
我如何根据上述条件修改以下方法来过滤小部件?
public IList<Widget> GetWidgets(string url) {
return _session
.Where(w => w.Urls.Contains(url))
.ToList();
}
理想情况下,我想使用linq查询,它只能访问数据库一次。我很感激你的帮助。感谢
答案 0 :(得分:1)
我设法通过添加自己的通配符匹配生成器来解决这个问题。有关如何注册生成器的示例,请参阅http://sentinel101.wordpress.com/2010/12/30/extend-nhibernate-linq-for-regex-matching/。这是任何人都感兴趣的发电机:
public class WildCardMatchGenerator : BaseHqlGeneratorForMethod {
public WildCardMatchGenerator() {
var methodDefinition = ReflectionHelper.GetMethodDefinition(() => WildCardMatchExtensions.WildCardMatch(null, null, ','));
SupportedMethods = new[] { methodDefinition };
}
public override HqlTreeNode BuildHql(MethodInfo method, Expression targetObject, ReadOnlyCollection<Expression> arguments, HqlTreeBuilder treeBuilder, IHqlExpressionVisitor visitor) {
return treeBuilder.Equality(treeBuilder.MethodCall("[dbo].[WildCardMatch]", new[] {
visitor.Visit(arguments[0]).AsExpression(),
visitor.Visit(arguments[1]).AsExpression(),
visitor.Visit(arguments[2]).AsExpression()
}), treeBuilder.Constant(1));
}
}
这是WildCardMatch UDF:
CREATE FUNCTION [dbo].[WildCardMatch] (
@Pattern NVARCHAR(MAX),
@Input NVARCHAR(MAX),
@Separator NVARCHAR(5)
)
RETURNS BIT
AS
BEGIN
SET @Pattern = REPLACE(@Pattern, '*', '%')
DECLARE @RtnValue BIT
SELECT @RtnValue = CASE WHEN COUNT(*) > 0 THEN 1 ELSE 0 END FROM [dbo].[Split](@Pattern, @Separator) WHERE @Input LIKE [Data]
RETURN @RtnValue
END
它调用的Split函数(来自http://blogs.microsoft.co.il/blogs/itai/archive/2009/02/01/t-sql-split-function.aspx):
CREATE FUNCTION [dbo].[Split]
(
@RowData NVARCHAR(MAX),
@Separator NVARCHAR(MAX)
)
RETURNS @RtnValue TABLE
(
[Id] INT IDENTITY(1,1),
[Data] NVARCHAR(MAX)
)
AS
BEGIN
DECLARE @Iterator INT
SET @Iterator = 1
DECLARE @FoundIndex INT
SET @FoundIndex = CHARINDEX(@Separator, @RowData)
WHILE (@FoundIndex > 0)
BEGIN
INSERT INTO @RtnValue ([Data])
SELECT Data = LTRIM(RTRIM(SUBSTRING(@RowData, 1, @FoundIndex - 1)))
SET @RowData = SUBSTRING(@RowData, @FoundIndex + DATALENGTH(@Separator) / 2, LEN(@RowData))
SET @Iterator = @Iterator + 1
SET @FoundIndex = CHARINDEX(@Separator, @RowData)
END
INSERT INTO @RtnValue ([Data])
SELECT Data = LTRIM(RTRIM(@RowData))
RETURN
END
最后,您需要上述UDF的C#实现:
public static class WildCardMatchExtensions {
public static bool WildCardMatch(this string pattern, string input, char separator = ',') {
foreach (var str in pattern.Split(new char[] { separator }, StringSplitOptions.RemoveEmptyEntries)) {
if (Regex.IsMatch(input, Regex.Escape(str.Trim()).Replace("\\*", ".*")))
return true;
}
return false;
}
}
希望这有帮助。
答案 1 :(得分:0)
我认为SQL服务器不允许您使用IN来表示逗号分隔的字段值。您需要LIKE
(下面的SQL示例):
Urls LIKE '%_your_url_%'
Linq, Expressions, NHibernate and Like comparison可以帮助您翻译LIKE
到 Linq到NHibernate