blocks|key|859741|text|也许动态查询在您的情况下可以工作？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|859742|http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx|offset|length|859743|您可以将where子句字符串传递给服务，该服务将对其进行验证并将其转换为表达式|859744|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|33|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@$D|Q|E|R|1|S]]|A|$]]|$1|F|3|G|5|6|7|T|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|U|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|C]]]]

Perhaps a dynamic query would work in your situation?

<a href="http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx" rel="noreferrer">http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx</a>

You would pass a where clause string to the service which would validate and convert it to an expression

blocks|key|642523|text|我们必须在LINQ中解决这个问题。例如，在执行LINQ-to-SQL时：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|642524|var+results+=+from+c+in+customers+where+c.City+==+"London"+select+c.Name;|code-block|syntax|javascript|642525|以某种方式，lambdas、c=>c.City+==+"London"和c=>c.Name的内容需要以服务器能够理解的形式在SQL+server上结束。显然，我们不能将lambda持久化到服务器。|offset|length|style|CODE|642526|相反，我们要做的是将lambda转换为表达式树，在运行时分析表达式树，从中构建一个实际的SQL字符串，并将该字符串发送到服务器进行处理。|642527|你可以做同样的事情。为您的服务器创建查询语言。在客户端，将lambda转换为表达式树。在运行时对它们进行分析，将结果转换为查询语言中的字符串，然后将查询发送到服务。|642528|如果你对它在LINQ中的工作原理感兴趣，LINQ-+to+-SQL架构师Matt+Warren已经写了一长串关于如何自己做这件事的博客文章：|642529|http://blogs.msdn.com/b/mattwar/archive/2008/11/18/linq-links.aspx|642530|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|E|L|10|9|0|0|0|0|0|1U|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|12|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|13|8|@$I|14|J|15|K|L]|$I|16|J|17|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|18|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|19|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1A|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|1B|8|@]|9|@$I|1C|J|1D|1|1E]]|A|$]]|$1|U|3|-4|5|6|7|1F|8|@]|9|@]|A|$]]]|V|$W|$5|X|Y|Z|A|$10|T]]]]

We have to solve this problem in LINQ-to-Just-About-Everything. For example, when doing LINQ-to-SQL:

<pre><code>var results = from c in customers where c.City == "London" select c.Name;
</code></pre>

somehow the content of the lambdas <code>c=&gt;c.City == "London"</code> and <code>c=&gt;c.Name</code> need to end up on the SQL server in a form the server understands. Clearly we cannot persist the lambdas to the server. 

Instead what we do is turn the lambdas into Expression Trees, analyze the expression trees at runtime, build an actual string of SQL out of it, and send that string to the server for processing.

You can do the same thing. Create a query language for your server. On the client side, turn the lambdas into expression trees. Analyze them at runtime, turn the result into a string in your query language, and then send the query to the service.

If you're interested in how this works in LINQ, the LINQ-to-SQL architect Matt Warren has written a long series of blog articles on how to do it yourself:

<a href="http://blogs.msdn.com/b/mattwar/archive/2008/11/18/linq-links.aspx" rel="noreferrer">http://blogs.msdn.com/b/mattwar/archive/2008/11/18/linq-links.aspx</a>

blocks|key|859933|text|我在CodePlex上使用this库来序列化/反序列化表达式树(但它是它的前一个版本)，它可以完成这项工作。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|859934|这里还有其他一些类似的问题：Serializing+and+Deserializing+Expression+Trees+in+C#|859935|entityMap|0|LINK|mutability|MUTABLE|url|http://expressiontree.codeplex.com/|1|https://stackoverflow.com/questions/217961/serializing-and-deserializing-expression-trees-in-c/1486253^0|D|4|0|0|E|1G|1|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]]|C|$]]|$1|F|3|-4|5|6|7|X|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|O]]]]

I use <a href="http://expressiontree.codeplex.com/" rel="nofollow noreferrer">this</a> library on CodePlex to serialize/deserialize Expression trees (but its previous version), and it does the work.

There are also some other similar questions here like this one:
<a href="https://stackoverflow.com/questions/217961/serializing-and-deserializing-expression-trees-in-c/1486253">Serializing and Deserializing Expression Trees in C#</a>

blocks|key|859967|text|创建一个Query+Object并将其传递给您的服务。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|859968|看看这是否有帮助：|859969|http://ruijarimba.wordpress.com/2011/05/09/entity-framework-and-t4-generate-query-objects-on-the-fly-part-1/|859970|举个例子：|859971|var+search+=+new+AlbumSearch();
search.PriceFrom+=+5;
search.PriceTo+=+10;
search.Artist+=+new+ArtistSearch(){+Name+=+"Metallica"+};
search.Genre+=+new+GenreSearch(){+NameContains+=+"Metal"+};

var+albuns+=+from+x+in+repository.All<Album>(search.GetExpression())
++++++++++++++++++select+x;|code-block|syntax|javascript|859972|entityMap|0|LINK|mutability|MUTABLE|url|http://martinfowler.com/eaaCatalog/queryObject.html|1^0|4|C|0|0|0|0|30|1|0|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@$A|Y|B|Z|1|10]]|C|$]]|$1|D|3|E|5|6|7|11|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|12|8|@]|9|@$A|13|B|14|1|15]]|C|$]]|$1|H|3|I|5|6|7|16|8|@]|9|@]|C|$]]|$1|J|3|K|5|L|7|17|8|@]|9|@]|C|$M|N]]|$1|O|3|-4|5|6|7|18|8|@]|9|@]|C|$]]]|P|$Q|$5|R|S|T|C|$U|V]]|W|$5|R|S|T|C|$U|G]]]]

Create a <a href="http://martinfowler.com/eaaCatalog/queryObject.html" rel="nofollow" title="Query Object">Query Object</a> and pass it to your services.

See if this helps:

<a href="http://ruijarimba.wordpress.com/2011/05/09/entity-framework-and-t4-generate-query-objects-on-the-fly-part-1/" rel="nofollow">http://ruijarimba.wordpress.com/2011/05/09/entity-framework-and-t4-generate-query-objects-on-the-fly-part-1/</a>

An example:

<pre><code>var search = new AlbumSearch();
search.PriceFrom = 5;
search.PriceTo = 10;
search.Artist = new ArtistSearch(){ Name = "Metallica" };
search.Genre = new GenreSearch(){ NameContains = "Metal" };

var albuns = from x in repository.All&lt;Album&gt;(search.GetExpression())
 select x;
</code></pre>

My current project is using the IDesign architecture, so all of my layers are services. I wanted to have my Read method in the CRUD of my resource access layer take a predicate in the form of a lambda expression as well as a list of related objects to pull. This way the resource access layer will be very generic.

<pre><code>[OperationContract]
Result&lt;MyObject&gt; ReadObjects(Func&lt;MyObject, bool&gt; predicate, string[] includes);
</code></pre>

Now I have come to discover something that should have been obvious, and that is that I cannot serialize lambda expressions. I looked into parsing a string into a lambda expression, but that is a no go as well.

Is there any method that I can use to pass a lambda expression to a service? Is there a better way to do what I am trying to do?

How can I pass a lambda expression to a WCF service?

服务器

我当前的项目使用的是IDesign架构，所以我所有的层都是服务。我想让资源访问层CRUD中的Read方法接受lambda表达式形式的谓词，以及要拉取的相关对象列表。这样，资源访问层将非常通用。[OperationContract]Result<MyObject> ReadObjects(Func<MyObject, b...

问如何将lambda表达式传递给WCF服务？
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问如何将lambda表达式传递给WCF服务？EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问如何将lambda表达式传递给WCF服务？
EN