如何根据提供的属性名称订购NHibernate 3.0 Linq查询(How to order a NHibernate 3.0 Linq query based on a supplied property name)

我正在尝试根据存储在字符串变量中的列名动态地命令我的NHibernate 3.0 Linq查询。

// The value of this variable can be the name of any property of Document. string columnName = "column1"; var query = from n in Session.Query<Document>() where n.DocumentNumber == documentNumber // how to order by the value of columnName? select n;

orderby关键字确实接受字符串（或变量），但是当我执行以下操作时：

var query = from n in Session.Query<Document>() where n.DocumentNumber == documentNumber orderby columnName select n;

我得到这个例外：

无法执行查询

select TOP (@p0) accumulate0_.Id as Id9_, accumulate0_.DocumentNumber as Documen10_9_ from dbo.Documents accumulate0_ where accumulate0_.DocumentNumber=@p1 order by @p2 desc

由ORDER BY编号1标识的SELECT项包含一个变量，作为标识列位置的表达式的一部分。 只有在引用列名的表达式进行排序时，才允许使用变量。

我知道有LINQ动态查询库 ，它提供了.OrderBy扩展方法的重载，它接受一个字符串 但显然只能在内存中工作 。 但是在使用NHibernate 3.0时会引发异常。

我试图让生成的SQL查询中的ORDER BY语句指定了适当的列名，所以我需要留在NHibernate领域。

使用NHibernate标准，我可以动态订购，但由于我使用的是NHibernate Linq，我似乎无法访问条件功能。

I'm trying to order my NHibernate 3.0 Linq query dynamically, based on a column name stored in a string variable.

// The value of this variable can be the name of any property of Document. string columnName = "column1"; var query = from n in Session.Query<Document>() where n.DocumentNumber == documentNumber // how to order by the value of columnName? select n;

The orderby keyword does accept a string (or variable) but when I execute the following:

var query = from n in Session.Query<Document>() where n.DocumentNumber == documentNumber orderby columnName select n;

I get this exception:

could not execute query

select TOP (@p0) accumulate0_.Id as Id9_, accumulate0_.DocumentNumber as Documen10_9_ from dbo.Documents accumulate0_ where accumulate0_.DocumentNumber=@p1 order by @p2 desc

The SELECT item identified by the ORDER BY number 1 contains a variable as part of the expression identifying a column position. Variables are only allowed when ordering by an expression referencing a column name.

I know there's the LINQ Dynamic Query Library which provides an overload of the .OrderBy extention method that accepts a string but that obviously only works in memory . It throws an exception when using NHibernate 3.0 however.

I'm trying to have the ORDER BY statement in the generated SQL query have the appropriate column name specified, so I need to stay in the NHibernate realm.

Using NHibernate criteria, I can order dynamically but since I'm using NHibernate Linq, I don't seem to have access to criteria features.

最满意答案

动态LINQ适用于任何源，而不仅仅是内存。

这就是我们现在正在使用的。

Dynamic LINQ works with any source, not just in memory.

That's what we are using right now.

如何根据提供的属性名称订购NHibernate 3.0 Linq查询(How to order a NHibernate 3.0 Linq query based on a supplied property name)

我正在尝试根据存储在字符串变量中的列名动态地命令我的NHibernate 3.0 Linq查询。

// The value of this variable can be the name of any property of Document. string columnName = "column1"; var query = from n in Session.Query<Document>() where n.DocumentNumber == documentNumber // how to order by the value of columnName? select n;

orderby关键字确实接受字符串（或变量），但是当我执行以下操作时：

var query = from n in Session.Query<Document>() where n.DocumentNumber == documentNumber orderby columnName select n;

我得到这个例外：

无法执行查询

select TOP (@p0) accumulate0_.Id as Id9_, accumulate0_.DocumentNumber as Documen10_9_ from dbo.Documents accumulate0_ where accumulate0_.DocumentNumber=@p1 order by @p2 desc

由ORDER BY编号1标识的SELECT项包含一个变量，作为标识列位置的表达式的一部分。 只有在引用列名的表达式进行排序时，才允许使用变量。

我知道有LINQ动态查询库 ，它提供了.OrderBy扩展方法的重载，它接受一个字符串 但显然只能在内存中工作 。 但是在使用NHibernate 3.0时会引发异常。

我试图让生成的SQL查询中的ORDER BY语句指定了适当的列名，所以我需要留在NHibernate领域。

使用NHibernate标准，我可以动态订购，但由于我使用的是NHibernate Linq，我似乎无法访问条件功能。

I'm trying to order my NHibernate 3.0 Linq query dynamically, based on a column name stored in a string variable.

// The value of this variable can be the name of any property of Document. string columnName = "column1"; var query = from n in Session.Query<Document>() where n.DocumentNumber == documentNumber // how to order by the value of columnName? select n;

The orderby keyword does accept a string (or variable) but when I execute the following:

var query = from n in Session.Query<Document>() where n.DocumentNumber == documentNumber orderby columnName select n;

I get this exception:

could not execute query

select TOP (@p0) accumulate0_.Id as Id9_, accumulate0_.DocumentNumber as Documen10_9_ from dbo.Documents accumulate0_ where accumulate0_.DocumentNumber=@p1 order by @p2 desc

The SELECT item identified by the ORDER BY number 1 contains a variable as part of the expression identifying a column position. Variables are only allowed when ordering by an expression referencing a column name.

I know there's the LINQ Dynamic Query Library which provides an overload of the .OrderBy extention method that accepts a string but that obviously only works in memory . It throws an exception when using NHibernate 3.0 however.

I'm trying to have the ORDER BY statement in the generated SQL query have the appropriate column name specified, so I need to stay in the NHibernate realm.

Using NHibernate criteria, I can order dynamically but since I'm using NHibernate Linq, I don't seem to have access to criteria features.

最满意答案

动态LINQ适用于任何源，而不仅仅是内存。

这就是我们现在正在使用的。

Dynamic LINQ works with any source, not just in memory.

That's what we are using right now.