nullable object must have a value

Question

There is paradox in the exception description: Nullable object must have a value (?!)

This is the problem:

I have a DateTimeExtended class, that has

{
  DateTime? MyDataTime;
  int? otherdata;

}

and a constructor

DateTimeExtended(DateTimeExtended myNewDT)
{
   this.MyDateTime = myNewDT.MyDateTime.Value;
   this.otherdata = myNewDT.otherdata;
}

running this code

DateTimeExtended res = new DateTimeExtended(oldDTE);

throws an InvalidOperationException with the message:

Nullable object must have a value.

myNewDT.MyDateTime.Value - is valid and contain a regular DateTime object.

What is the meaning of this message and what am I doing wrong?

Note that oldDTE is not null. I've removed the Value from myNewDT.MyDateTime but the same exception is thrown due to a generated setter.

Strange. I reproduce the exception with the .Value there, and get no exception without the .Value there. Are you sure you're running the updated code? — Yuliy
– Yuliy, Commented Dec 13, 2009 at 11:20
The constructor takes an instance of itself. how are you creating that first instance? — Paul Creasey
– Paul Creasey, Commented Dec 13, 2009 at 11:23
it is constructed as new() without parameters, and then I add the values (it works). — Dani
– Dani, Commented Dec 13, 2009 at 13:09
Problem solved - the problem wasn't there... there was a generated setter to the otherdata and MyDateTime, that was checking the value before setting it.. flying when it's null !!! — Dani
– Dani, Commented Dec 13, 2009 at 15:30

Matt · Accepted Answer · 2017-12-14 09:59:52Z

273

You should change the line this.MyDateTime = myNewDT.MyDateTime.Value; to just this.MyDateTime = myNewDT.MyDateTime;

The exception you were receiving was thrown in the .Value property of the Nullable DateTime, as it is required to return a DateTime (since that's what the contract for .Value states), but it can't do so because there's no DateTime to return, so it throws an exception.

In general, it is a bad idea to blindly call .Value on a nullable type, unless you have some prior knowledge that that variable MUST contain a value (i.e. through a .HasValue check).

EDIT

Here's the code for DateTimeExtended that does not throw an exception:

class DateTimeExtended
{
    public DateTime? MyDateTime;
    public int? otherdata;

    public DateTimeExtended() { }

    public DateTimeExtended(DateTimeExtended other)
    {
        this.MyDateTime = other.MyDateTime;
        this.otherdata = other.otherdata;
    }
}

I tested it like this:

DateTimeExtended dt1 = new DateTimeExtended();
DateTimeExtended dt2 = new DateTimeExtended(dt1);

Adding the .Value on other.MyDateTime causes an exception. Removing it gets rid of the exception. I think you're looking in the wrong place.

edited Dec 14, 2017 at 9:59

Matt

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answered Dec 13, 2009 at 11:14

Yuliy

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4 Comments

Dani Over a year ago

You are right about the .value, yet something else causes the exception. I've removed the .value, and i've changed the code order of the constructor- copying the int value first, but same exception is thrown.

Dani Over a year ago

I've commented on the question - found the problem, it was in a generated setter for the properties.

adnan Over a year ago

yes, its resolved my problem, i just change null able object to non null able, and convert datetime to string directly, not by datetimeobject.value.datetime.tostring()

DVK Over a year ago

Great answer. Getting an exception calling .Value on a null object makes sense (I guess), but the exception message is really misleading if you happen to be dealing with two Nullable objects. Something like 'The .Value property requires the object to be non-null' would make a whole lot more sense.

Jeremy Thompson · Accepted Answer · 2024-11-26 10:27:57Z

29

When using LINQ extension methods (e.g. Select, Where), the lambda function might be converted to SQL that might not behave identically to your C# code. For instance, C#'s short-circuit evaluated && and || are converted to SQL's eager AND and OR. This can cause problems when you're checking for null in your lambda.

Example:

MyEnum? type = null;
Entities.Table.Where(a => type == null || 
    a.type == (int)type).ToArray();  // Exception: Nullable object must have a value

Example 2:

IQueryable<LocationSummary> query = from locations in 
context.Locations join devices in context.Devices on locations.Id equals devices.LocationId
select new LocationSummary
{
 LocationId = locations.Id,
 Device.SKU = devices.SKU ?? "Unknown",  <-- could be null
 LastData = locations.Samples.Any()   <-- if its null, make it a nullable datatype and then you can give it nulls
   ? locations.Samples.Max(x => x.EndTime)
   : (DateTimeOffset)null
};

edited Nov 26, 2024 at 10:27

Jeremy Thompson

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answered Jan 21, 2015 at 13:23

Protector one

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2 Comments

Protector one Over a year ago

I realize this answer is not relevant to the OP's specific case, but it's relevant to the Exception he's getting. Also, this page is the first hit on Google for that exception, which makes it relevant.

BobtheMagicMoose Over a year ago

This was also this issue for me with null-conditional operators ("optional chaining" in Javascript) . Instead of obj?.getValue(), I needed to do obj != null && obj.getValue()

ArunPratap · Accepted Answer · 2019-08-19 17:07:35Z

9

Try dropping the .value

DateTimeExtended(DateTimeExtended myNewDT)
{
   this.MyDateTime = myNewDT.MyDateTime;
   this.otherdata = myNewDT.otherdata;
}

edited Aug 19, 2019 at 17:07

ArunPratap

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answered Dec 13, 2009 at 11:12

Paul Creasey

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1 Comment

Dani Over a year ago

doesn't help. it throws the same exception if I run the 2nd line first.

O'Rooney · Accepted Answer · 2023-11-26 20:52:17Z

5

To answer your actual question, what does "Nullable object must have a value " mean?

It is actually saying "You are trying to take the .Value of a nullable object, but it is null so that can't be done.".

I think that it is a terribly-written error message. They could have just said "Nullable object must have a value in order to take it's .Value"

edited Nov 26, 2023 at 20:52

answered Apr 27, 2023 at 5:29

O'Rooney

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1 Comment

Eike Over a year ago

I agree the exception message is terribly written. The very gist of a nullable object is that it does not have to have a value!

Cecil Has a Name · Accepted Answer · 2009-12-13 11:13:25Z

2

Assign the members directly without the .Value part:

DateTimeExtended(DateTimeExtended myNewDT)
{
   this.MyDateTime = myNewDT.MyDateTime;
   this.otherdata = myNewDT.otherdata;
}

answered Dec 13, 2009 at 11:13

Cecil Has a Name

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Comments

Lee · Accepted Answer · 2009-12-13 11:13:32Z

2

In this case oldDTE is null, so when you try to access oldDTE.Value the InvalidOperationException is thrown since there is no value. In your example you can simply do:

this.MyDateTime = newDT.MyDateTime;

answered Dec 13, 2009 at 11:13

Lee

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1 Comment

Dani Over a year ago

The oldDTE is not null, but I removed the value anyhow... it is still throwing that exception....

MSH · Accepted Answer · 2023-09-12 06:30:47Z

Use

`DateTimeExtended(DateTimeExtended myNewDT)
{
   this.MyDateTime = myNewDT.MyDateTime.**GetValueOrDefault();**
   this.otherdata = myNewDT.otherdata;
}`

It'll simply check the value and set Null if there is no value.

> .Value

Must only be used when you are sure it's coming. But as you are not sure, you simply use ".GetValueOrDefault()"

Explanation:

DateTimeExtended(DateTimeExtended myNewDT) is a constructor for the DateTimeExtended class, which takes another DateTimeExtended object myNewDT as a parameter.
this.MyDateTime = myNewDT.MyDateTime.GetValueOrDefault(); assigns the value of myNewDT.MyDateTime to the MyDateTime property of the current instance.GetValueOrDefault() is used to safely handle situations where myNewDT.MyDateTime might be null. If myNewDT.MyDateTime is null, this method will return the default value for the DateTime type (which is DateTime.MinValue).
this.otherdata = myNewDT.otherdata; assigns the otherdata property of the current instance with the value from myNewDT.otherdata`, assuming that other data is a non-nullable property.

This constructor is designed to ensure that the MyDateTime property of the new instance is never null. It assigns a default value to MyDateTime if myNewDT.MyDateTime is null, making the code safer to use when you are not sure whether myNewDT.MyDateTime will have a value or not.

Pavel Radzivilovsky · Accepted Answer · 2009-12-13 11:14:43Z

0

Looks like oldDTE.MyDateTime was null, so constructor tried to take it's Value - which threw.

answered Dec 13, 2009 at 11:14

Pavel Radzivilovsky

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Comments

Juris · Accepted Answer · 2012-09-28 13:19:36Z

0

I got this message when trying to access values of a null valued object.

sName = myObj.Name;

this will produce error. First you should check if object not null

if(myObj != null)
  sName = myObj.Name;

This works.

answered Sep 28, 2012 at 13:19

Juris

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1 Comment

newfurniturey Over a year ago

Before answering, please try to read through the other answers for the question first - especially the accepted answer that states exactly what you placed in your answer. Though it doesn't show it using code, it spells it out. Also, try to make your example code relevant to the question's - such as this.MyDateTime = myNewDT.MyDateTime.Value;, not sName = myObj.Name;

KKG · Accepted Answer · 2020-07-08 07:10:22Z

0

I got this solution and it is working for me

if (myNewDT.MyDateTime == null)
{
   myNewDT.MyDateTime = DateTime.Now();
}

answered Jul 8, 2020 at 7:10

KKG

1

Comments

Ogglas · Accepted Answer · 2023-11-30 22:33:10Z

0

I got this exception using EF Core 7.x:

System.InvalidOperationException: Nullable object must have a value.

With this code:

Updated = new[] { x.Updated, x.Threats.Max(tac => tac.Updated) }.Max()

Changed new[] to List<DateTime?> and then it worked:

Updated = new List<DateTime?> { x.Updated, x.Threats.Max(tac => tac.Updated) }.Max()

answered Nov 30, 2023 at 22:33

Ogglas

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Comments

simaglei · Accepted Answer · 2025-11-19 12:10:12Z

0

You get this exception if you're casting a nullable DateTime to a non-nullable DateTime if the nullable DateTime is in fact null:

DateTime? nullableDateTime = null;
DateTime nonnullableDateTime = (DateTime)nullableDateTime;

Solution - again: Check if (nullableDateTime != null) before casting.

answered 2 days ago

simaglei

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