按日期类型以匿名类型对对象进行排序的好方法？

Question

I have the following code:

var resultArticles = from a in articleItems 

select new
{
   Title = a.Title, 
   ArticleDate = a[Constants.FieldNames.ArticleStartDate] != null ?
     ((DateTime)a[Constants.FieldNames.ArticleStartDate]).ToString(Constants.Date.Format): string.Empty,
   ByLine = a[Constants.FieldNames.Byline],
   FileRef = SPUtility.ConcatUrls(web.Url, a.Url)
};

var sortedArticles = resultArticles.OrderBy(a => a.ArticleDate).ToList();

rptArticles.DataSource = sortedArticles;
rptArticles.DataBind();

I guess there must be a better way to sort/order here because if I have the dates (dd/mm/yyy)

12.01.2011
11.02.2011
10.02.2011
13.01.2011
08.02.2011

it only sorts by the day and don't take the month into consideration so the result in sortedArticles is as follows:

08.01.2011
10.02.2011
11.02.2011
12.01.2011
13.01.2011

I obviously want to display the latest article first, ie 11.02.2011

Any suggestions?

Thanks in advance.

Answer 1

The problem is that in your Select, you're calling ToString on your date field. As a result ArticleDate is being projected as a string . This is why it's not sorting correctly.

Projecting the ArticleDate as a nullable Date is probably your best bet

var resultArticles = from a in articleItems 
select new
{
   Title = a.Title, 
   ArticleDate = a[Constants.FieldNames.ArticleStartDate] != null ?
     ((DateTime)a[Constants.FieldNames.ArticleStartDate]) : default(DateTime?),
   ByLine = a[Constants.FieldNames.Byline],
   FileRef = SPUtility.ConcatUrls(web.Url, a.Url)
};

Also, for something simple like this, you can use the more concise "dot notation"

var resultArticles = articleItems.Select(a => new { 
   Title = a.Title, 
   ArticleDate = a[Constants.FieldNames.ArticleStartDate] != null ?
     ((DateTime)a[Constants.FieldNames.ArticleStartDate]) : default(DateTime?),
   ByLine = a[Constants.FieldNames.Byline],
   FileRef = SPUtility.ConcatUrls(web.Url, a.Url)
};

At this point you can sort this collection by ArticleDate, which will be stored as a true Date, instead of a string

resultArticles.OrderBy(a => a.ArticleDate).ToList();

Answer 2

Use the following syntax

var q = from el in dataSource orderby el.SortField select new { 
    //your projection
};

The point here is to sort during the selection in one query.

By using this statement you sort by actual DateTime and project string representation.