nhibernate queryover LIKE与表达式树 [英] nhibernate queryover LIKE with expression trees

问题描述

我想在我的基本存储库类中添加一个方法，允许我使用 LIKE 表达式，但是我不太确定该怎么做.我想创建一个通用方法，该方法查看传入的表达式树，并在传入的字符串值中查找通配符.然后将相应地生成QueryOver语句.

I'm looking to add a method to my base repository class that allows me to use LIKE expressions but I'm not quite sure of how to go about this. I want to create a generic method that looks at the expression tree passed in and looks for wildcard characters in the string values passed in. It would then generate the QueryOver statement accordingly.

我目前有以下内容:

public IList<T> FindAll(Expression<Func<T, bool>> criteria, char wildCard)
{
    return SessionFactory.GetCurrentSession()
            .QueryOver<T>()
            .Where(criteria)
            .List();
}

显然，困难的部分尚未到来.我需要浏览表达式树并动态地使用QueryOver建立查询.寻找一些有关如何进行此操作的指示.还是我只是在这里浪费时间，应该在我的存储库中创建用于处理 Like 查询的单个方法?

Obviously the hard part is yet to come. I need to look through the expression tree and build the query using QueryOver dynamically. Looking for some pointers on how to proceed with this. Or am I just wasting my time here and should just create individual methods in my repositories that handle the LIKE queries?

理想情况下，我想告诉您以下两者之间的区别:

Ideally I'd like to tell the difference between the following:

• 搜索*
• *搜索
• *搜索*

因此生成的查询将是:

• 像搜索％"这样的字段
• 像％search"这样的字段
• 像％search％"这样的字段

推荐答案

有两种方法在QueryOver中编写Like表达式.

There's two ways to write a Like expression in QueryOver.

如果您在Where子句中这样做:

If you do it off the Where clause:

.Where(Restrictions.Like(Projections.Property<T>(*projected property*), *string value*, MatchMode.Anywhere))

但是，这有点长.

因此您可以使用WhereRestrictionOn:

So you can use WhereRestrictionOn:

.WhereRestrictionOn(*projected property*).IsLike(*string value*, MatchMode.Anywhere)

这意味着您需要传递两个参数，例如:

This means you need to pass in two parameters like:

FindAll<User>(x => x.FirstName, "bob");

您也许可以使用.Contains，.StartsWith，.EndsWith，但我不确定.

You may be able to use .Contains, .StartsWith, .EndsWith, but I'm not sure.

FindAll<User>(x => x.FirstName.Contains("bob"));
FindAll<User>(x => x.FirstName.StartsWith("bob"));
FindAll<User>(x => x.FirstName.EndsWith("bob"));

我认为这些内容在NHibernate中不起作用.

I don't think those work in NHibernate.

希望有帮助.

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