如何使用Linq从C＃中的void语句返回数据

问题描述：

我是LINQ的新手，并且没有太多使用此方法的经验。

我遇到的问题是我有一个void函数，想要使用LINQ返回一些数据。

代码：

Hi,

I am new to LINQ and do not have much experience using this method.

The problem I have come across is where I have a void function and want to return some data back using LINQ.

the code:

private void Test(string a, string b, string c, bool d, bool o, bool f, DateTime g, DateTime h, string i, string j, string k)
{
if (b != "")
var query = from a in PromoSuffixDispaly
                                    where a.MasterSuffixCode == a.MasterSuffixCode && a.PromoSuffixCode == a.PromoSuffixCode && a.Pds_ItemType == "N" && a.Code.Substring(a.Code.Length - 1, 7) != a.orderAs_Product && a.Pds_DeletedIndicator == false
                                    && !(from a0 in PromoSuffixDispaly
                                         where a0.MasterSuffixCode == a0.MasterSuffixCode && a0.PromoSuffixCode == a0.PromoSuffixCode
                                         select new { a0.Pds_NatItemNumber }).ToString().Contains(a.Pds_NatItemNumber = a.BusinessUnit + " " + a.orderAs_Product)
                                    select new { a };
}

此查询运行但所有数据都被恢复。并且RETURN语句将无效。我可以使用的任何建议或方式吗？

谢谢

从解决方案中添加：

当我放置断点并将鼠标悬停在查询后它没有显示任何内容，但在屏幕上显示所有数据被带回。

- OriginalGriff

[/ edit]

this query runs but all the data is brought back. and the RETURN statement will not work in a void. any suggestion or way that I can use?

thanks

[edit]
Added from "solution":
when I put my break point and hover over the query after it shows nothing, but on the screen all the data is brought back.
- OriginalGriff
[/edit]

答

你不能在 void 方法中使用 return 返回任何值 - 因为声明方法为 void 明确地说这个方法没有返回值 - 所以外部世界在调用方法时不能期待任何回复。

如果如果要返回值，则需要更改方法的签名：要么包含返回类型，要么添加 out 或 ref 该方法可以设置为包含返回值的参数。

对于像你这样的Linq查询，你可能想回来IEnumerable< T>或者列表< T>

我无法确切地建议你想要返回什么类型 - 我不知道PromoSuffixDispaly包含什么类型 - 但你可以返回该类型的IEnumerable，或者使用在该IEnumerable上的ToList方法将其转换为List< T>然后返回。

You cannot use return in a void method to return any value - becasue declaring a method as void is explicitly saying "this method does no return a value" - so the outside world cannot expect anything back when it calls the method.

If you want to return a value, you need to change the "signature" of your method: either to include a return type, or to add an out or ref parameter which the method can set to contain the return values.

In the case of a Linq Query such as yours, you probably want to return an IEnumerable<T> or a List<T>
I can't suggest exactly what type you want to return - I don't know what type PromoSuffixDispaly contains - but you could return the IEnumerable of that type, or use the ToList method on that IEnumerable to convert it to a List<T> and return that.

如何使用Linq从C＃中的void语句返回数据

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