C# Convert Nullable DateTime in String with mask into Select New

Question

I must to retry a nullable Datetime from an Entity Framework and convert it in a Masked string of this type: ToString("dd-MM-yyyy")

I retry all the value with this code(now i show the only DataLead)

 var dbResult = conc.Clientes.Where(x => x.StatoCliente == "1").ToList();
                var leads = from e in dbResult
                            select new
                            { 
                              e.DataLead
                            } into selectedLead
                            select selectedLead;
                return Json(leads, JsonRequestBehavior.AllowGet);

In other part of my code i do the conversion with this code:

 DateTime date = (DateTime) DataLead;
 string dateElaborated = date.ToString("dd-MM-yyyy");

But, how can i do this operation in my LINQ selection function?

Thanks to all

Is `e.DataLead` your nullable date? What do you want to happen if it's null? — rory.ap, Jul 22 '16 at 13:38
Yes, it's my nullable date. If it's null i can't return an empty string or null — Roberto Mindoli, Jul 22 '16 at 13:42

score 1 · Accepted Answer · answered Jul 22 '16 at 15:26

You can use string.Format (suppose e.DateLead is nullable DateTime type):

var dbResult = conc.Clientes.Where(x => x.StatoCliente == "1").ToList();
var leads = from e in dbResult
    select new
    {
        Datalead = string.Format("{0:dd-MM-yyyy}", e.DataLead)
    };

Or the new feature in C# 6

var leads = from e in dbResult
    select new
    {
        Datalead = e.DataLead?.Value.ToString("dd-MM-yyyy")
    };

score 0 · Answer 2 · edited Jul 22 '16 at 21:13

0

var leads = from e in dbResult
            select new {
                selectedLead = e.DataLead != null ? e.DataLead.ToString("dd-MM-yyyy"): string.Empty
            };

edited Jul 22 '16 at 21:13

oɔɯǝɹ

7,219
7
58
69

answered Jul 22 '16 at 13:42

Hitesh Thakor

471
2
12

You are missing the ? – RIanGillis Jul 22 '16 at 13:44
No, that won't compile. If not for any other reason as there is no such thing as `nulle`. – rory.ap Jul 22 '16 at 13:46
Also, the preferred way to check if a nullable is null is with `HasValue`. – rory.ap Jul 22 '16 at 13:47
I have try it but doesn't work. I have an error on ":" - it ask me the } – Roberto Mindoli Jul 22 '16 at 13:48
Actually scratch what I just said. Proof: http://stackoverflow.com/questions/676078/which-is-preferred-nullable-hasvalue-or-nullable-null – rory.ap Jul 22 '16 at 13:48
Although this code may be help to solve the problem, providing additional context regarding _why_ and/or _how_ it answers the question would significantly improve its long-term value. Please [edit] your answer to add some explanation. – oɔɯǝɹ Jul 22 '16 at 21:12

Oliver · Answer 3 · 2016-07-22T13:52:03.227

0

How about this:

// Get alternative text if DataLead is null
var leads = dbResult.Select(entry => entry.DataLead)
                    .Select(date => date.HasValue 
                                    ? date.Value.ToString("dd-MM-yyyy") 
                                    : "unknown");

// Get only entries where DataLead is not null.
var leads = dbResult.Select(entry => entry.DataLead)
                    .Where(entry => entry.HasValue)
                    .Select(date => date.Value.ToString("dd-MM-yyyy"));

edited Jul 22 '16 at 13:52

answered Jul 22 '16 at 13:46

Oliver

43,366
8
94
151

Thanks but i use Select New because i need to load a lot of parameters...for simplicity i have write only DataLead, but I have almost 20 dates to be loaded – Roberto Mindoli Jul 22 '16 at 13:51

score 0 · Answer 4 · answered Jul 22 '16 at 13:47

0

var leads = conc.Clientes
    .Where(o => o.StatoCliente == "1" && o.DataLead.HasValue)
    .Select(o => o.DataLead.Value.ToString("dd-MM-yyyy"))
    .ToList();

Simple and clear. Also, I'd strongly advise to not use string literals like "1", but introduce an enum or a const value.

answered Jul 22 '16 at 13:47

Phronux

125
1
9

Thanks but i use Select New because i need to load a lot of parameters...for simplicity i have write only DataLead, but I have almost 20 dates to be loaded – Roberto Mindoli Jul 22 '16 at 13:50
So check all the dates and get their values. And try to be more specific next time. – Phronux Jul 22 '16 at 13:53

C# Convert Nullable DateTime in String with mask into Select New

4 Answers4