选择模板 [英] Select template

问题描述

是否可以在LINQ查询中为SELECT创建模板?现在，我有6方法使用完全相同的SELECT，如果可能的话，我想使用模板.

Is it possible to make a template for SELECT in a LINQ query? Right now I have 6 methods that uses the exact same SELECT, i would like to use a template if possible.

这是我正在使用的代码，当我想更改选择内容时，必须在代码中的很多地方更改相同的内容.

This is the code I'm using, when I want to make a change to the select I have to change the same thing at so many places in my code.

result = query.Select(b => new
{
    route_id = b.b.route_id,
    name = b.b.name,
    description = b.b.description,
    distance = b.b.distance,
    distance_to_route = (int)b.distance_to_from_me,
    departure_place = b.b.departure_place,
    arrival_place = b.b.arrival_place,
    owner = b.b.user.username,
    average_rating = b.avg_rating,
    is_favorite = b.is_favorite,
    date = b.b.date,
    attributes = b.b.route_attributes.Select(c => 
        c.route_attribute_types.attribute_name),
    coordinates = b.b.coordinates.Select(c => 
        new coordinateToSend { sequence = c.sequence, 
            lat = c.position.Latitude, 
            lon = c.position.Longitude })
});

推荐答案

以下是您可以执行此操作的一种简单示例:

Here is a simple example of one way you could do this:

在您的示例中，您正在将源类型转换为匿名类型.您可以创建一个类来表示您的转换/结果类型，例如:

In your example, you're converting the source type to an anonymous type. You could create a class to represent your converted/result type, for example:

    public class ResultClass
    {
        public string ResultPropA { get; set; }
    }

为示例起见，可以说以下是您的源类的定义:

For examples sake, lets say the following was the definition of your source class:

    public class SourceClass
    {
        public string SourcePropA { get; set; }
    }

现在，您已经为源和结果对象提供了类型定义，您可以创建一个扩展方法，将源类的集合转换为结果类的集合:

Now that you have type definitions for your source and result objects, you can create an extension method to convert a collection of your source class to a collection of your result class:

    public static class SourceToResultRepository
    {
        public static IEnumerable<ResultClass> ConvertSourceToResult
            (this IEnumerable<SourceClass> source)
        {
            return source.Select(s => new ResultClass
            {
                ResultPropA = s.SourcePropA
                //Add all other property transformations here
            });
        }
    }

下面是一个如何在需要执行转换的地方使用它的示例:

And here is an example of how you could use it wherever you need to perform the transformation:

 //Extension usage:
 var result = Database.Source.ConvertSourceToResult();

 //Direct usage:
 var result = SourceToResultRepository.ConvertSourceToResult(Database.Source);

这篇关于选择模板的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！