Question

使用C＃linq查询，我想获得按ID和更新时间排名的日期。 id：包含在列表'idList'中 updatetime：datatime的类型

示例数据：

查询：

.onecenter{text-align:center;width:150px;}

<table  border="1" cellspacing="0" cellpadding="0">
    <tr >
        <td class='onecenter'>id</td>
        <td class='onecenter'>updatetime</td>
    </tr>
    <tr >
        <td class='onecenter'>1</td>
        <td class='onecenter'>2016-02-16</td>
    </tr>
    <tr >
        <td class='onecenter'>2</td>
        <td class='onecenter'> 2016-02-14</td>
    </tr>
    <tr>
        <td  class='onecenter'>3</td>
        <td  class='onecenter'>2016-02-15</td>
    </tr>
    <tr>
        <td class='onecenter'>4</td>
        <td  class='onecenter'>2016-02-17</td>
    </tr>
</table>

IDLIST：

2,3

结果应为：

    .onecenter{text-align:center;width:150px;}

    <table  border="1" cellspacing="0" cellpadding="0">
        
        <tr >
            <td class='onecenter'>id</td>
            <td class='onecenter'>updatetime</td>
        </tr>
       <tr>
            <td  class='onecenter'>3</td>
            <td  class='onecenter'>2016-02-15</td>
        </tr>
        <tr >
            <td class='onecenter'>2</td>
            <td class='onecenter'> 2016-02-14</td>
        </tr>
        <tr>
            <td class='onecenter'>4</td>
            <td  class='onecenter'>2016-02-17</td>
        </tr>
        <tr >
            <td class='onecenter'>1</td>
            <td class='onecenter'>2016-02-16</td>
        </tr>
        
       
    </table>

如何通过linq查询获得结果。

我试过了：

var data1 = query.Where(m => idList.Contains(m.ID)).OrderByDescending(x => x.updatetime);
var data2 = query.Where(m => !idList.Contains(m.ID)).OrderByDescending(x => x.updatetime);
var date = data1.Concat(data2).ToList();

和：

var data = query.GroupBy(m => idList.Contains(m.ID)).OrderByDescending(x => x.updatetime);

但它没有得到正确的结果。

Answer 1

我会使用此查询：

var result = query.OrderByDescending(q => idList.Contains(q.ID) ? 1 : 0)
                  .ThenByDescending(q => q.updatetime);

Answer 2

尝试使用：

Except

使用data1为第二个删除[2016-02-17 06:22:04.167 UTC] 3 2/15/2016 12:00:00 AM [2016-02-17 06:22:04.169 UTC] 2 2/14/2016 12:00:00 AM [2016-02-17 06:22:04.170 UTC] 4 2/17/2016 12:00:00 AM [2016-02-17 06:22:04.170 UTC] 1 2/16/2016 12:00:00 AM中已有的内容，然后您就可以获得此内容：

IEnumerable

修改

如果您的数据很多，您可以考虑将项目保留为List，直到您需要处理它而不是将其更改为var data1 = query.Where(x => idList.Contains(x.ID)).OrderByDescending(y => y.UpdateTime); var data2 = query.Except(data1).OrderByDescending(y => y.UpdateTime); var data = data1.Concat(data2); //don't change to List here foreach(var dat in data){ //use it by fetching it one by one like this }。这可能会节省一些时间：

List<String> messagelist = new ArrayList<>(); try { AmazonSQS sqs = new AmazonSQSClient(credentials); Region usWest2 = Region.getRegion(Regions.US_WEST_2); sqs.setRegion(usWest2); boolean flag = true; while(flag) { ReceiveMessageRequest receiveMessageRequest = new ReceiveMessageRequest(queuename); receiveMessageRequest.setMaxNumberOfMessages(number_of_message_); receiveMessageRequest.withMaxNumberOfMessages(number_of_message_).withWaitTimeSeconds(wait_time_second_); List<Message> messages = sqs.receiveMessage(receiveMessageRequest).getMessages(); for (Message message : messages) { // System.out.println(" Body: " + message.getBody()); messagelist.add( message.getBody()); String messageReceiptHandle = message.getReceiptHandle(); sqs.deleteMessage(new DeleteMessageRequest().withQueueUrl(queuename).withReceiptHandle(messageReceiptHandle)); } if(messages.size()==0) { flag = false; } } } catch (AmazonServiceException ase) { ase.printStackTrace(); } catch (AmazonClientException ace) { ace.printStackTrace(); } finally { return messagelist ; }

C＃linq查询排名由两个条件组成

2 个答案: