将匿名类型声明为数组以保留范围 [英] Declaring anonymous type as array correctly to keep scope

问题描述

所有我想做的是正确地声明 var place ，所以一旦我到达 foreach 循环。我假设我需要在如果连接的语句之前声明它。这是一个正确的假设，如果是这样，我如何声明它？谢谢！

All I want to do is declare var place correctly so it is still in scope once I get to the foreach loop. I'm assuming I need to declare it before the if statement for connections. Is this a correct assumption and if so how do I declare it? Thanks!

using (var db = new DataClasses1DataContext())
        {
            if (connections == "Connections")
            {
                var place = (from v in db.pdx_aparts
                             where v.Latitude != null && v.Region == region && v.WD_Connect >= 1
                             select new
                             {
                                 locName = v.Apartment_complex.Trim().Replace(@"""", ""),
                                 latitude = v.Latitude,
                                 longitude = v.Longitude
                             }).Distinct().ToArray();
            }
            else
            {
                var place = (from v in db.pdx_aparts
                             where v.Latitude != null && v.Region == region &&    ((v.WD_Connect == null) || (v.WD_Connect == 0))
                             select new
                             {
                                 locName = v.Apartment_complex.Trim().Replace(@"""", ""),
                                 latitude = v.Latitude,
                                 longitude = v.Longitude
                             }).Distinct().ToArray();

            }

            foreach (var result in place)
            ....

推荐答案

您可以使用单个条目创建一个数组，其值稍后忽略：

You can create an array with a single entry whose value you ignore later:

// Note: names *and types* must match the ones you use later on.
var place = new[] { new { locName = "", latitude = 0.0, longitude = 0.0 } };
if (connections = "Connections")
{
    // Note: not a variable declaration
    place = ...;
}
else
{
    place = ...;
}

这是因为每次使用匿名类型都使用具有相同名称和类型的属性，以相同的顺序，将使用相同的具体类型。

This works because every use of anonymous types using properties with the same names and types, in the same order, will use the same concrete type.

我认为最好只让代码不同它需要：

I think it would be better to make the code only differ in the parts that it needs to though:

var query = v.db.pdx_aparts.Where(v => v.Latitude != null && v.Region == region);
query = connections == "Connections"
    ? query.Where(v => v.WD_Connect >= 1)
    : query.Where(v => v.WD_Connect == null || v.WD_Connect == 0);
var places = query.Select(v =>  new
                          {
                              locName = v.Apartment_complex
                                         .Trim()
                                         .Replace("\"", ""),
                              latitude = v.Latitude,
                              longitude = v.Longitude
                          })
                  .Distinct()
                  .ToArray();

这里更容易说明只有部分取决于 connections value是处理 WD_Connect 的查询部分。

Here it's much easier to tell that the only part which depends on the connections value is the section of the query which deals with WD_Connect.

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