如何获取通用列表中的最后一个对象？

发布于 2024-08-06 05:32:47 字数 450 浏览 1 评论 0原文

我将填充的 SelectList 传递到我的视图，并且希望将所选值默认为列表中的最后记录。到目前为止，我得到了：

IQueryable<BuildNumber> projBuildNos = tcRepository.GetProjectBuildNos();
BuildList = new SelectList(projBuildNos, "ID", "value", projBuildNos.Last().ID);

我收到一个异常，说“不支持查询运算符‘Last’，但我似乎无法获取通用列表中的最后一条记录，也找不到任何示例。

此代码来自一个“表单视图模型”将选择列表从我的存储库传递回视图，我认为我应该在这里执行此操作，但是我对 generics/mvc/linq 很陌生，因此很高兴获得其他建议

。如果您需要更多信息，请告诉我。

原文

I am passing a populated SelectList to my View and I want to default the selected value to the last record in the list. So far I've got:

IQueryable<BuildNumber> projBuildNos = tcRepository.GetProjectBuildNos();
BuildList = new SelectList(projBuildNos, "ID", "value", projBuildNos.Last().ID);

I get an exception saying "the query operator 'Last' is not supported but I can't seem to get at the last record in my generic list and can't find any examples.

This code is from a 'form view model' passing select lists from my repository back to the view and I think I should be performing this here. However I'm new to generics/mvc/linq so am happy for alternative suggestions.

Thanks in advance for any help. Please let me know if you want any more info.

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故人如初 2024-08-13 05:32:47

您是否已经将查询的所有结果吸入内存？如果是这样，我建议您执行查询并将结果放入列表中：

List<BuildNumber> projBuildNos = tcRepository.GetProjectBuildNos().ToList();
BuildList = new SelectList(projBuildNos, "ID", "value", projBuildNos.Last().ID);

否则您很容易得到执行查询两次的解决方法 - 可能会给出不一致的结果。

Are you already going to suck all the results from your query into memory? If so, I suggest you execute your query and get the result into a list:

List<BuildNumber> projBuildNos = tcRepository.GetProjectBuildNos().ToList();
BuildList = new SelectList(projBuildNos, "ID", "value", projBuildNos.Last().ID);

Otherwise you could easily end up with a workaround which executes the query twice - possibly giving inconsistent results.

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