CODEWITHSUNDEEP
c#asp.net-mvclinq-to-sql
Novkovski Stevo Bato
Novkovski Stevo Bato

Reputation: 1043

Linq to SQL - order by two columns

I have two columns, "date added" and "date modified".

I want to order all products by date modified, but since it can be null i want to get date added in that case.

 var q = from c in db.Products
                where c.UserID == UserID
                orderby c.DateModified ?? c.DateAdded descending
                select
                    new ManageProducts
                        {
                            ID = c.ID,
                            Image = c.Photo.PhotoFile,
                            Name = c.Name,
                            DateAdded = (DateTime) c.DateModified ?? c.DateAdded 
};

This show me an error on 

DateAdded = (DateTime) c.DateModified ?? c.DateAdded

Error

Upvotes: 1

Views: 157

Answers (2)

Ilya Ivanov
Ilya Ivanov

Reputation: 23646

try remove the cast (DateTime) in 

DateAdded = (DateTime) c.DateModified ?? c.DateAdded

I've wrote snippet and in works fine

var sample = new [] {new {Nul = (int?) 5,    Val = 6}, 
                     new {Nul = (int?) null, Val = 6}};

var res = from value in sample 
          orderby value.Nul ?? value.Val
          select new {Val = value.Nul ?? value.Val};

Just to make sure:

Console.WriteLine (typeof(int) == res.ElementAt(0).Val.GetType()); //True
Console.WriteLine (typeof(int?) == res.ElementAt(0).Val.GetType()); //False

Upvotes: 1

Fedor Hajdu
Fedor Hajdu

Reputation: 4695

Use

DateAdded = c.DateModified.HasValue ? c.DateModified.Value : c.DateAdded

You're trying to assign nullable DateTime (c.DateModified) to a non-nullable DateTime field (DateAdded). You must take the value from nullable property if it exists or use another value (in your case c.DateAdded)

Upvotes: 1

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