LINQ returns System.Data.SqlTypes.SqlNullValueException. Why?

Question

LINQ returns System.Data.SqlTypes.SqlNullValueException. Why?

Corey Fleig 530

I'm learning LINQ, and trying to fetch data from a SQL Server database. All I'm trying to do is fetch data from one datetime field that is defined as nullable, where I know the field value is set to null.

Here's my statement:

var query = from cm in mydb.myTable
where cm.key == 1
select cm.ADMDATE;

But this won't execute because it returns EntityQueryable. So I changed the statement:

var query = (from cm in mydb.myTable
where cm.key == 1
select cm.ADMDATE).FirstOrDefault();

This is where I get the runtime error: System.Data.SqlTypes.SqlNullValueException: 'Data is Null. This method or property cannot be called on Null values.' So I tried a suggestion from AI:

var query = (from cm in mydb.myTable
where cm.key == 1
select new myClass
{
   myDate = cm.ADMDATE.HasValue ? c.ADMDATE.Value : (DateTime?)null
}).FirstOrDetault();

You guessed it! .HasValue won't compile.

Any recommendations on how to get LINQ to execute?

Corey Fleig 530 Reputation points

2026-01-14T22:56:02.38+00:00

The AI answer does NOT solve the problem. The error occurs when the LINQ statement is run, so there's no point checking the result - its too late. Also, if I need to fetch 10 fields, and only 1 field is null, this AI solution is also no help.
Viorel 127.3K Reputation points

2026-01-14T23:18:42.7633333+00:00
It seems that it has been resolved:

https://learn.microsoft.com/en-us/answers/questions/5707294/
Corey Fleig 530 Reputation points

2026-01-15T00:07:40.51+00:00

I unaccepted the original question. Sorry about that. I thought it was answered by AI, but it turns out there's plenty of problems. So this second iteration of the question is more comprehensive.
Viorel 127.3K Reputation points

2026-01-15T00:15:52.2966667+00:00

I think that the error related to .HasValue means that ADMDATE is not nullable. (For example, it is DateTime, not DateTime?). Try to get details about ADMDATE.

Answer accepted by question author

0 additional answers

Your answer

Corey Fleig 530 Reputation points

2026-01-14T22:56:02.38+00:00

The AI answer does NOT solve the problem. The error occurs when the LINQ statement is run, so there's no point checking the result - its too late. Also, if I need to fetch 10 fields, and only 1 field is null, this AI solution is also no help.
Viorel 127.3K Reputation points

2026-01-14T23:18:42.7633333+00:00

It seems that it has been resolved:

https://learn.microsoft.com/en-us/answers/questions/5707294/
Corey Fleig 530 Reputation points

2026-01-15T00:07:40.51+00:00

I unaccepted the original question. Sorry about that. I thought it was answered by AI, but it turns out there's plenty of problems. So this second iteration of the question is more comprehensive.
Viorel 127.3K Reputation points

2026-01-15T00:15:52.2966667+00:00

I think that the error related to .HasValue means that ADMDATE is not nullable. (For example, it is DateTime, not DateTime?). Try to get details about ADMDATE.

Answer 1

Hello @Corey Fleig ,

I suspect your entity class (the one mapped to your database table) likely has a non-nullable DateTime property. You should look for the entity class that your myTable DbSet uses:

public class YourTableEntity  
{
    public int Id { get; set; }
    public DateTime? somedate { get; set; }  // ← Added nullable
}

And the result class should correctly define the DateTime property as nullable as well:

public class myClass
{
    public DateTime? MyDate { get; set; }
}

Everything else is the same as before, you can even query for NULL values without any issues:

var query = from c in myTable
            where Id == 1
            select new myClass { myDate = c.somedate };

var result = query.FirstOrDefault();
if (result?.myDate.HasValue == true)
{
    Console.WriteLine($"Date: {result.myDate.Value}");
}
else
{
    Console.WriteLine("Date is NULL");
}

var nullRecords = from c in myTable
                  where c.somedate == null
                  select new myClass { myDate = c.somedate };

If you still face issues, please share the relevant parts of your entity class and the result class so I can help you further.

Corey Fleig 530 Reputation points

2026-01-20T22:41:33.36+00:00

thank you so much - you nailed it!
Anonymous

2026-01-21T02:03:04.11+00:00

Glad to hear that you have resolved the issue. If you have any questions, feel free to reach out anytime.