C# Nullable to string

Question

I have a DateTime? variable, sometimes the value is null, how can I return an empty string "" when the value is null or the DateTime value when not null?

score 111 · Answer 1 · answered Sep 18 '09 at 18:01

111

Though many of these answers are correct, all of them are needlessly complex. The result of calling ToString on a nullable DateTime is already an empty string if the value is logically null. Just call ToString on your value; it will do exactly what you want.

answered Sep 18 '09 at 18:01

Eric Lippert

647,829
179
1,238
2,067

5

Unless you want to use the DateTime properties like `.Day` `.Week` because that will give you the entire DateTime string and lose the power of the DateTime class. e.g. `myVariable.Value.Hour.ToString()`. Just an example reason why you might want to do otherwise. – baron Aug 04 '11 at 06:01
2

@baron, those properties aren't `Nullable`. – Sam Sep 10 '13 at 04:37

Jon Seigel · Accepted Answer · 2009-09-18T20:36:53.860

41

string date = myVariable.HasValue ? myVariable.Value.ToString() : string.Empty;

edited Sep 18 '09 at 20:36

answered Sep 18 '09 at 17:09

Jon Seigel

12,251
8
58
92

16

What!? You can just call .ToString() on the Nullable instance to get String.Empty. Even Eric Lippert (who might have even implemented this behavior) notes this. _That_ should be the accepted answer. – codekaizen Jul 09 '10 at 01:48
1

@codekaizen - I get an exception when I try that. So no, that would not be the accepted answer. Perhaps this is not a problem in more recent versions of c# or .net? – Kimball Robinson Aug 20 '10 at 16:13
1

@k.robinson - perhaps that is because you are using a boxed reference to the instance. Please realize that I'm advocating the same as Eric Lippert - one of the creators of the .Net platform itself - is pointing out in his answer. If you have a problem, you might want to reconsider if "select isn't broken" (http://www.pragprog.com/the-pragmatic-programmer/extracts/tips). – codekaizen Aug 20 '10 at 16:57
@codekaizen - Ok. I still wish I could do this without a typecast: dateTimeField.Text = dateTimeObj.HasValue ? ((DateTime) dateTimeObj).ToShortDateString() : string.Empty; – Kimball Robinson Aug 25 '10 at 00:12

score 18 · Answer 3 · answered Sep 18 '09 at 17:17

18

Actually, this is the default behaviour for Nullable types, that without a value they return nothing:

public class Test {
    public static void Main() {
        System.DateTime? dt = null;
        System.Console.WriteLine("<{0}>", dt.ToString());
        dt = System.DateTime.Now;
        System.Console.WriteLine("<{0}>", dt.ToString());
    }
}

this yields

<>
<2009-09-18 19:16:09>

answered Sep 18 '09 at 17:17

Joey

344,408
85
689
683

4

+1 Did not know this. However, you cannot supply a formatting string this way. – Jon Seigel Sep 18 '09 at 17:20
Hm, right. Though this may not be a problem in this case. I didn't know this myself too until yesterday, though. Stumbled over it when looking at `Nullable` in Reflector :-) – Joey Sep 18 '09 at 17:27

score 8 · Answer 4 · edited May 19 '16 at 14:35

8

Calling .ToString() on a Nullable<T> that is null will return an empty string.

edited May 19 '16 at 14:35

marsze

15,079
5
45
61

answered Sep 18 '09 at 20:40

DJ.

1,005
2
15
24

score 7 · Answer 5 · answered Sep 18 '09 at 17:10

7

You could write an extension method

public static string ToStringSafe(this DateTime? t) {
  return t.HasValue ? t.Value.ToString() : String.Empty;
}

...
var str = myVariable.ToStringSafe();

answered Sep 18 '09 at 17:10

JaredPar

733,204
149
1,241
1,454

4

Or better yet: make it generic: `public static string ToSafeString(this T? obj) where T : struct` :) – JulianR Sep 18 '09 at 17:51
Holy smokes, didn't realize .NET had this ability! – tster Sep 18 '09 at 18:45

score 3 · Answer 6 · answered Jul 30 '17 at 09:55

3

All you need to do is to just simply call .ToString(). It handles Nullable<T> object for null value.

Here is the source of .NET Framework for Nullable<T>.ToString():

public override string ToString() {
    return hasValue ? value.ToString() : "";
}

answered Jul 30 '17 at 09:55

Jalal

6,594
9
63
100

score 2 · Answer 7 · answered Sep 18 '09 at 17:09

2

DateTime? d;
// stuff manipulating d;
return d != null ? d.Value.ToString() : String.Empty;

answered Sep 18 '09 at 17:09

Cecil Has a Name

4,962
1
29
31

score 1 · Answer 8 · edited Oct 09 '11 at 17:56

1

DateTime? MyNullableDT;
....
if (MyNullableDT.HasValue)
{
    return MyNullableDT.Value.ToString();
}
return "";

edited Oct 09 '11 at 17:56

NullUserException

83,810
28
209
234

answered Sep 18 '09 at 17:09

Ahmed Khalaf

1,220
12
28

score 1 · Answer 9 · edited Oct 09 '11 at 17:56

1

if (aDate.HasValue)
    return aDate;
else
    return string.Empty;

edited Oct 09 '11 at 17:56

NullUserException

83,810
28
209
234

answered Sep 18 '09 at 17:09

Mike

5,437
7
45
62

score 1 · Answer 10 · answered Sep 18 '09 at 17:10

1

DateTime d?;
string s = d.HasValue ? d.ToString() : string.Empty;

answered Sep 18 '09 at 17:10

Patrick Desjardins

136,852
88
292
341

score 0 · Answer 11 · edited Jun 19 '19 at 01:19

0

According to Microsoft's documentation:

The text representation of the value of the current Nullable object if the HasValue property is true, or an empty string ("") if the HasValue property is false.

edited Jun 19 '19 at 01:19

Cody Gray - on strike

239,200
50
490
574

answered Jun 18 '19 at 16:04

David Zhang

39
2

This was already answered [here](https://stackoverflow.com/a/1446033/10927863) by [Eric Lippert](https://stackoverflow.com/users/88656/eric-lippert) – Eliahu Aaron Jun 18 '19 at 16:13

C# Nullable to string

11 Answers11

Linked