动态生成LINQ查询 [英] Dynamically generate LINQ queries

问题描述

我们有一个对象

public class SomeObject
{
   public Name {get;set;}
   public City {get;set;}
   public State {get;set}
   //various other parameters.  Let's say there's ~20
}

是否可以动态创建新的LINQ查询没有源$ C ​​$ C重新编译？相反，查询参数来自存储和在数据库中更新的XML结构

Is it possible to dynamically create new LINQ queries without recompilation of source code? Instead, the query parameters come from an XML structure that is stored and updated in the database.

var result = from i in someObj
             where 
             //XML requests Name = 'Bob'...so append this where clause
             name = 'Bob'

可以这样做？

推荐答案

下面是与前pression树的解决方案：

Here is a solution with expression trees:

var param = Expression.Parameter(typeof(SomeObject), "p");
var exp = Expression.Lambda<Func<SomeObject, bool>>(
    Expression.Equal(
        Expression.Property(param, "Name"),
        Expression.Constant("Bob")
    ),
    param
);
var query = someObj.Where(exp);

我知道这是要复杂得多，但您可以在次是有用的。

I know it's much more complex, but this may be useful in times.

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