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问题描述
我有这样的对象:
public class MyObject{
public int Prop1 {get;set;}
}
我正在做一个linq到SQL查询，该查询返回这样的myObject列表:
var TheQuery = from ....
where ....
select new MyObject()
{
Prop1 = (...... ).Sum( d => d)
}.ToList();
问题是prop1是一个子查询的总和，有时可能没有返回，总和为null，不能分配给prop1，因为它是int.
这是一个好方法.
感谢您的建议.
推荐答案
如何使用范围变量:
var TheQuery = from ....
where ....
let subquery = (...... )
select new MyObject()
{
Prop1 = subquery!=null ? (subquery.Sum( d => d) ?? 0) : 0;
}.ToList();
其他推荐答案
我只会将您的财产提升为int?.您一无所有，最好将其表示为零.理由是，应该有可能拥有一个实际的总和为0.在这种情况下，您没有实际值的总和，因此保持无效结果允许您保留此差异.
否则，您可能会考虑(假设查询将值返回可作为空的)在结果中调用.GetValueOrDefault()，这将在数字类型的情况下将null值正常化为0.
问题描述
I have an object like this:
public class MyObject{
public int Prop1 {get;set;}
}
I'm doing a linq to sql query that returns a list of MyObject like this:
var TheQuery = from ....
where ....
select new MyObject()
{
Prop1 = (...... ).Sum( d => d)
}.ToList();
The problem is that Prop1 is a sum of a subquery and sometimes there might be nothing returned and the Sum is null, which can't be assigned to Prop1 because it's an int.
What's a good way around this.
Thanks for your suggestions.
推荐答案
how about using a range variable:
var TheQuery = from ....
where ....
let subquery = (...... )
select new MyObject()
{
Prop1 = subquery!=null ? (subquery.Sum( d => d) ?? 0) : 0;
}.ToList();
其他推荐答案
I would simply promote your property to an int?. You have the sum of nothing, it's best to represent that as a null. The rationale is that it should be possible to have an actual sum that is 0. In this case, you do not have a sum of actual values, so keeping the null result allows you to preserve this difference.
Otherwise, you might consider (assuming the query returns the value as a nullable) invoking .GetValueOrDefault() on the result, which would normalize a null value to 0 in the case of a numeric type.
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