Nhibernate ICriteria和在查询中使用Lambda表达式 [英] Nhibernate ICriteria and Using Lambda Expressions in queries

问题描述

我是NHibernate的新手，我有些困惑.

hi i am new in NHibernate and i am a little confused.

假设我们有一个 product 表. 假设 product 表具有2列price1和price2.

Suppose we have a product table. Let the product table have 2 columns price1 and price2.

然后我可以通过HQL查询映射的产品实体，如下所示:

then i may query mapped product entities via HQL as follows:

string queryString = @"from product p
where p.price1 = p.price2 + 100 ";
IList result = session.CreateQuery(queryString).List();

如何通过ICriteria API实现这一目标.

How can i achieve that via ICriteria API.

我知道这很荒谬，但我正在尝试……

i know it's absurd but i am trying sth like that:

session.CreateCriteria(typeof(product))
   .Add(Expression.Eq("price1", "price2" + 100))
   .List()

或更恰当的说(使用lambda扩展名):

or more appropriately sth like that (using lambda extensions):

session.CreateCriteria(typeof(product))
   .Add<product>(p => p.price1 == (p.price2 + 100))
   .List()

事实上，我从googlecode下载了lambda扩展项目，并对其进行了扩展以可回避地处理Binary和Unary表达式，以实现诸如以下的表达式:

in fact i downloaded lambda extensions project from googlecode and i extended it to recusively process Binary and Unary expressions to implement expresssions like:

session.CreateCriteria(typeof(product))
   .Add<product>(p => 
               (!(p.price1 > 29007) && (p.price1 > 19009)) 
            || (p.price2 == 29009));

我目前正在像上面那样处理查询，但是由于我无法返回适当的限制条件来获取所需的条件，所以arithmethic子句让我很烦.

i am currently processing queries like above but the arithmethic clauses are annoying me since i can't return the appropriate Restriction to obtain the Criterion i need.

mpffh我已经厌倦了试图以一种全面的方式来解释它.我希望它能奏效.感谢您的帮助.

mpffh i m tired of trying to explain it in a comprehensive way. i hope it worked. Any help is appreciated.

推荐答案

您可以尝试以下方法:

ISQLFunction sqlAdd = new VarArgsSQLFunction("(", "+", ")");
var products = session
    .CreateCriteria<product>()
    .Add(
        Expression.EqProperty(
            "price1", 
            Projections.SqlFunction(
                sqlAdd, 
                // TODO: replace this with appropriate type
                NHibernateUtil.Double,
                Projections.Property("price2"),
                Projections.Constant(100) 
            )
        )
    )
    .List<product>();

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