Datetime? to string

Question

I need to convert a Datetime? to a string. The ?? operator dosent work and calling tostring on a null would make things fall over. Any advice on how to handle datetime? Thanks

Below is my code for context. o.CustomerRequiredDate is a Datetime? and PredictedActivationDate is a string. Both need to stay as the datatype they currently are.

 {
       rsp = (from r in db.btRequests
                                      join o in db.NewOrders
                                      on r.ID equals o.RequestId
                                      join s in db.Status
                                      on r.Status equals s.ID.ToString()
                                      select new DataLayer.OrderResponse
                                      {
                                          RequestID = requestID,
                                          Message = s.StatusDescription,
                                          OrderStatus = r.Status.ToString(),
                                          PredictedActivationDate =r.Status == "3" || r.Status == "4" || r.Status == "5"
                                          || r.Status == "6" || r.Status == "9" ? (o.CustomerRequiredDate ?? ""): ""

                                      }).FirstOrDefault();

http://stackoverflow.com/questions/1445766/c-nullabledatetime-to-string — Paolo Moretti, Jul 21 '11 at 15:34
General observation, btRequests' `Status` field is holding a `string` yet stores `"3"`, `"4"` - should probably be an `int` field. — Kieren Johnstone, Jul 21 '11 at 15:35
@Kieren Johnstone This is a generic webservice across a few diffrent ordering platforms. Status isnt always an int — Tom Squires, Jul 21 '11 at 16:11

score 7 · Accepted Answer · edited Jul 21 '11 at 15:34

7

You could do

o.CustomerRequiredDate.HasValue ? o.CustomerRequiredDate.Value.ToString() : ""

edited Jul 21 '11 at 15:34

Yuck

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answered Jul 21 '11 at 15:33

Samuel Béliveau

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+1 The trick is in using the `Value` property instead of just the object on its own. – Yuck Jul 21 '11 at 15:34
On the left of ':' you have a DateTime and a string on the right of ':' It doesn't work! – Guillaume Jul 21 '11 at 15:36
The result of `Nullable.ToString` is already an empty string if the value is null, you can simply write `o.CustomerRequiredDate.ToString()` – Paolo Moretti Jul 21 '11 at 15:42
I think the .Value approach is valid, especially if he eventually wants to use the other .ToString overloads related to DateTime class. – Samuel Béliveau Jul 21 '11 at 15:45
Wow, thatnks for all your quick replys – Tom Squires Jul 21 '11 at 15:46

Guillaume · Answer 2 · 2011-07-21T15:39:56.133

6

o.CustomerRequiredDate.ToString()

It returns an empty string for a DateTime? with a null value and the DateTime.ToString otherwise.

edited Jul 21 '11 at 15:39

answered Jul 21 '11 at 15:34

Guillaume

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score 3 · Answer 3 · answered Jul 21 '11 at 15:34

3

I'm assuming o.CustomerRequiredDate is your DateTime?.

Try

o.CustomerRequiredDate.HasValue ? o.CustomerRequiredDate.ToString() : string.Empty

instead.

answered Jul 21 '11 at 15:34

CassOnMars

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score 3 · Answer 4 · answered Jul 21 '11 at 15:35

3

o.CustomerRequiredDate.HasValue ? o.CustomerRequiredDate.Value.ToString() : string.Empty

answered Jul 21 '11 at 15:35

Berial

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score 2 · Answer 5 · answered Jul 21 '11 at 15:37

Outside of SQL for moment, Nullable<T>.ToString() is documented to return an empty string if HasValue is false (ie., it "is null").

If you are concerned that the statements

DateTime? date = null;
string output = date.ToString();

will "fall over," fear not. Of course, if using the expression in Linq, it would be up to the provider (-to-SQL, -to-EF), to behave properly.

score 1 · Answer 6 · answered Jul 21 '11 at 15:40

A nullable value is never null in the sense that you can't use ToString on it:

o.CustomerRequiredDate.ToString()

However, you might want a different result than the default empty string for a null value:

o.CustomerRequiredDate.HasValue ? o.CustomerRequiredDate.Value.ToString() : "No date"

Datetime? to string

6 Answers6