Ошибка nullable object must have a value

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.

Nullable object must have a value is an “InvalidOperationException” shown by the compiler in the C Sharp programming language (C#) when you don’t adhere to the rules of a nullable data type. The root causes of this error vary and we’ll teach you why it occurs and how to fix it in technologies like Entity Framework and Language-Integrated Query (LINQ).

This means all that you’ll learn will give you a better understanding of the “Nullable” type in C Sharp and how to prevent the “InvalidOperationException”.

Now, launch your code editor, and let’s fix your code together.

Why the C Sharp Compiler Says a Nullable Object Must Have a Value

The C Sharp compiler says a nullable object must have a value because of the following:

• Your database value is null
• You compared “HasValue” to null
• You accessed the value of a Nullable type
• You assigned null to a non-nullable property
• A data extension column is not nullable

– Your Database Value Is Null

When your database column value contains null and you try to retrieve it and use it at the same time, that’s when the C Sharp compiler will throw an exception. This happens because null values have a special treatment in C Sharp, and you can’t treat them like other data types.

For example, the following code wants to retrieve the value of “x.trv” from the database using “x.trv.Value”. This should work if “x.trv” contains data, but C Sharp will throw an exception if it’s null.

– You Compared “Hasvalue” To Null

When you compare the “HasValue” property of a variable to “null” in C Sharp, the compiler will throw an “InvalidOperationException” if the value of the variable is “null”. The “HasValue” property returns Boolean “true” if the variable contains a value and Boolean “false” if it’s null.

So when you compare it with a variable that’s “null”, you’ll start an invalid operation that’s not allowed in C Sharp. For example, the following code has a variable “null_int” with a value “null” and later the code compares its “HasValue” property to “null”.

The execution of this code will lead to the “InvalidOperationException” when you compile the code on your computer. Or, you can copy the code and paste it on SharpLab online C Sharp playground to see the results in real time.

– You Accessed the Value of a Nullable Type

Accessing the value of a Nullable type will cause the nullable object must have a value linq exception. The same applies in a C Sharp code that does not involve LINQ and the next code is an example.

In the code, the variable “null_integer” has a “null” value, and later the code calls the “Value” property to retrieve this “null” property. This is an invalid operation and the C Sharp compiler will throw the “InvalidOperationException”.

– You Assigned Null to a Non-nullable Property

When your code assigns null to a non-nullable property in your model in Entity Framework, that’s when you’ll get the nullable object must have a value Entity Framework exception. This will happen if a query can return null if there is no result, then it assigns this null value to the non-nullable property.

This will cause the C Sharp compiler to raise an exception because it’s an invalid operation. Moreover, the nullable object must have a value meaning from the entire exception message that you’ll notice will show that it originates from “System.InvalidOperationException”.

– A Data Extension Column Is Not Nullable

A data extension column that is not nullable is why you’re getting the nullable object must have a value Marketing Cloud exception. With such a column, you’ll write a SQL INSERT or SELECT query with the assumption that the column is nullable.

As a result, the query will attempt to insert null data into the column, and C Sharp will raise an exception as a sign that you’ve performed an invalid operation. That’s because if it’s not nullable, it must contain data and it cannot be null.

How To Fix the Nullable Object Must Have a Value Exception in C Sharp

You can fix the Nullable Object Must Have a Value Exception in C Sharp using the following:



• Use “GetValueOrDefault()” on uncertain values
• Don’t compare HasValue to null
• Use “HasValue” in a conditional statement
• Don’t assign null to non-nullable property
• Mark your data extension column as nullable

– Use “Getvalueordefault()” On Uncertain Values

You can use the “GetValueOrDefault()” method to retrieve a value that might be null. This will the case for a database column and you can apply the same approach to solve the nullable object must have a value guid c# exception.

The following is a rewrite of our sample database connection code that raised the exception. This time, we use the “GetValueOrDefault()” to prevent the C Sharp compiler from raising the exception.

– Don’t Compare “Hasvalue” To Null

When a variable in your code holds a “null” value, don’t use the “HasValue” property to compare it again with “null”. This will prevent an exception from the C Sharp compiler because it’ll consider it a valid operation. In the following code, we updated a previous code that compared “HasValue” to “null”.

We deleted the comparison code and when you run the code, it will compile without an exception and you can use the same approach to fix the nullable object must have a value datetime exception.

– Use “Hasvalue” in a Conditional Statement

Using the “HasValue” property of a variable that holds “null” will prevent the C Sharp compiler from throwing an exception. With this, you can setup an “if” condition statement that’ll check if the variable has a value that you can use.

If not, you can write a custom message in the “else” part of the “if” statement. The following code is how this works and it’s a rewrite of a previous code that tried to retrieve a variable that contained a “null” value.

– Don’t Assign Null to Non-nullable Property

Anywhere in your code, don’t assign null to a non-nullable property. When you adhere to this, you’ll prevent the nullable object must have a value int c# exception in your code. If you’re getting this exception in the model in Entity Framework, comment out each line of code until it works.

– Mark Your Data Extension Column as Nullable

If you want to send null values to a data column in the Marketing Cloud data extension, ensure you mark or set the column as nullable. By doing this, the C Sharp compiler will not raise an exception because you’ll be sending null values to a column that can accept them.

Conclusion

This article explained why the C Sharp compiler will raise an exception that a nullable object in your code must have a value. Afterward, we detailed how to handle the exception and we’ll leave you with the following:

• “Nullable object must have a value” occurs if you don’t handle null data the correct way in C Sharp.
• Comparing the “HasValue” property to “null” will raise the “InvalidOperationException” in C Sharp.
• You can use the “HasValue” property or “GetValueOrDefault()” to prevent the “InvalidOperationException” when working with a null data type in C Sharp.

At this stage, you are a better C Sharp developer and you know it. Happy coding and don’t forget to share our article!

References

• https://learn.microsoft.com/en-us/dotnet/api/system.nullable-1.hasvalue?view=net-7.0
• https://learn.microsoft.com/en-us/dotnet/api/system.invalidoperationexception?view=net-7.0
• https://learn.microsoft.com/en-us/dotnet/api/system.nullable-1.getvalueordefault?view=net-7.0
• https://learn.microsoft.com/en-us/dotnet/api/system.management.propertydata.value?view=dotnet-plat-ext-7.0

I have the following query:

var query = DbContext.TripSegments
    .Where(ts => ts.RailcarTrip.WaybillRailcar.Waybill.CompanyCode == companyCode &&
        ts.IsLoaded && ts.EndDate == null &&
        ts.DestinationCity == city && ts.DestinationState == state);

//query = query
//    .GroupBy(ts => ts.RailcarTrip.WaybillRailcar.RailcarNumber)
//    .Select(x => x.First());

int count = await query.CountAsync();

This query works just fine. But if I uncomment the two commented lines, I get an exception.

System.InvalidOperationException: Nullable object must have a value.

RailcarTrip and WaybillRailcar are navigation fields using non-nullable foreign key columns. RailcarNumber is a non-nullable text column.

Beyond that, it’s a black box and I don’t know how else to narrow down which column or field is causing a problem. How would a person troubleshoot something like this?

More Information

The output window shows only this:

Exception thrown: 'System.InvalidOperationException' in System.Private.CoreLib.dll
Nullable object must have a value.

Here is my stack trace.

at System.ThrowHelper.ThrowInvalidOperationException_InvalidOperation_NoValue()
at System.Nullable`1.get_Value()
at Microsoft.EntityFrameworkCore.Query.SqlExpressions.SelectExpression.ClientProjectionRemappingExpressionVisitor.Visit(Expression expression)
at System.Linq.Expressions.ExpressionVisitor.VisitUnary(UnaryExpression node)
at System.Linq.Expressions.UnaryExpression.Accept(ExpressionVisitor visitor)
at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
at Microsoft.EntityFrameworkCore.Query.SqlExpressions.SelectExpression.ClientProjectionRemappingExpressionVisitor.Visit(Expression expression)
at Microsoft.EntityFrameworkCore.Query.SqlExpressions.SelectExpression.ApplyProjection(Expression shaperExpression, ResultCardinality resultCardinality, QuerySplittingBehavior querySplittingBehavior)
at Microsoft.EntityFrameworkCore.Query.Internal.SelectExpressionProjectionApplyingExpressionVisitor.VisitExtension(Expression extensionExpression)
at System.Linq.Expressions.Expression.Accept(ExpressionVisitor visitor)
at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
at Microsoft.EntityFrameworkCore.Query.RelationalQueryTranslationPostprocessor.Process(Expression query)
at Microsoft.EntityFrameworkCore.Query.QueryCompilationContext.CreateQueryExecutor[TResult](Expression query)
at Microsoft.EntityFrameworkCore.Storage.Database.CompileQuery[TResult](Expression query, Boolean async)
at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.CompileQueryCore[TResult](IDatabase database, Expression query, IModel model, Boolean async)
at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<>c__DisplayClass12_0`1.<ExecuteAsync>b__0()
at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQuery[TResult](Object cacheKey, Func`1 compiler)
at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.ExecuteAsync[TResult](Expression query, CancellationToken cancellationToken)
at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.ExecuteAsync[TResult](Expression expression, CancellationToken cancellationToken)
at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ExecuteAsync[TSource,TResult](MethodInfo operatorMethodInfo, IQueryable`1 source, Expression expression, CancellationToken cancellationToken)
at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ExecuteAsync[TSource,TResult](MethodInfo operatorMethodInfo, IQueryable`1 source, CancellationToken cancellationToken)
at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.CountAsync[TSource](IQueryable`1 source, CancellationToken cancellationToken)
at TTRailtrax.Controllers.InboundRailcarsController.<BuildInboundRailcars>d__2.MoveNext() in D:UsersjwoodsourcereposRailtraxTTRailtraxControllersInboundRailcarsController.cs:line 55

Include provider and version information

EF Core version: 6.0.1
Database provider: Microsoft.EntityFrameworkCore.SqlServer
Target framework: .NET 6.0
Operating system: Windows 11
IDE: Visual Studio 2022 17.0.4