Question

I’m encountering some peculiarities with LINQ to SQL.

With a relatively simple query, I want to select some fields, but have the date fields formatted as strings, which I first achieved like this:

        var list = dataContext.MyLists.Single(x => x.ID == myId);          var items = from i in list.MyItems                     select                         new                             {                                 i.ID,                                 i.Sector,                                 i.Description,                                 CompleteDate = i.CompleteDate.HasValue ? i.CompleteDate.Value.ToShortDateString() : '',                                 DueDate = i.DueDate.HasValue ? i.DueDate.Value.ToShortDateString() : ''                             };                                

Later on I tried the following query, which is exactly the same, except I’m querying straight from my dataContext, rather than an element in my first query:

        var items = from i in dataContext.MyLists                     select                         new                             {                                 i.ID,                                 i.Sector,                                 i.Description,                                 CompleteDate = i.CompleteDate.HasValue ? i.CompleteDate.Value.ToShortDateString() : '',                                 DueDate = i.DueDate.HasValue ? i.DueDate.Value.ToShortDateString() : ''                             }; 

The first one runs fine, yet the second query yields a:

Could not translate expression ‘…’ into SQL and could not treat it as a local expression.

If I remove the lines that Format the date, it works fine. If I remove the .HasValue check it also works fine, until there are null values.

Any ideas?

Anthony

Answer 1

I’d do the SQL part without doing the formatting, then do the formatting on the client side:

var items = list.MyItems.Select(item => new { item.ID, item.Sector, item.Description,                                                item.CompleteDate, item.DueDate })                         .AsEnumerable() // Don't do the next bit in the DB                         .Select(item => new { item.ID, item.Sector, item.Description,                                               CompleteDate = FormatDate(CompleteDate),                                               DueDate = FormatDate(DueDate) });   static string FormatDate(DateTime? date) {     return date.HasValue ? date.Value.ToShortDateString() : '' }