过滤逗号分隔的数据 [英] Filtering Comma Separated Data
问题描述
我的网站上有一堆小部件,我正在尝试根据传入的URL对其进行过滤.说一个小部件具有以下结构:
My site has a bunch of widgets and i'm trying to filter them based on the url which is passed in. Say a Widget has the following structure:
public class Widget {
public int Id { get; set; }
public string Name { get; set; }
public string Urls { get; set; }
}
其中Urls是用逗号分隔的列表,用于显示小部件的网址,例如:
Where Urls is a comma separated list for the urls where the widget should be displayed, e.g.:
/,/博客/,/博客/123,/新闻/*
/, /Blog/, /Blog/123, /News/*
新闻后面的星号表示只要传入的网址以/News/开头,就会选择该小部件.
The asterisk after News indicates the Widget will be selected whenever the passed in url starts with /News/.
如何根据我的上述条件修改以下方法以过滤窗口小部件?
How could i modify the following method to filter the widgets based on my conditions above?
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.非常感谢您的帮助.谢谢
Ideally i'd like to use a linq query and it must only hit the database once. I'd appreciate the help. Thanks
推荐答案
我通过添加自己的通配符匹配生成器设法解决了这个问题.参见 http://sentinel101.wordpress.com/2010/12/30/extend-nhibernate-linq-for-regex-matching/例如,如何注册生成器.如果有人感兴趣,这是生成器:
I managed to solve this by adding my own wild card match generator. See http://sentinel101.wordpress.com/2010/12/30/extend-nhibernate-linq-for-regex-matching/ for example of how to register the generator. Here's the generator incase anyone is interested:
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:
And here is the 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
以及它调用的Split函数(来自 http://blogs.microsoft.co.il/blogs/itai/archive/2009/02/01/t-sql-split-function.aspx ):
And the Split function it calls (from 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:
Lastly you'll need the C# implementation of the above UDF:
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;
}
}
希望这会有所帮助.
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