int value=0; if (value == 0) { value = null; } How can I set value to null above?
Any help will be appreciated.
6 Answers
In .Net, you cannot assign a null value to an int or any other struct. Instead, use a Nullable<int>, or int? for short:
int? value = 0; if (value == 0) { value = null; } Further Reading
4 Comments
Mahendran
I was trying to assign null from immediate window for debugging purpose. It didn't work though. How can this be achieved?
p.s.w.g
@mahemadhi probably for the same reason you can't do it in regular code. If a variable is declared as an
int, it cannot receive null as a value, even while debugging. You need to declare it as an int?.Mahendran
the variable is declared
nullable. Yet in immediate window, I couldn't assign null.
Kasim Husaini
cannot assign null value to "int?", getting System.InvalidOperationException
Additionally, you cannot use "null" as a value in a conditional assignment. e.g...
bool testvalue = false; int? myint = (testvalue == true) ? 1234 : null; FAILS with: Type of conditional expression cannot be determined because there is no implicit conversion between 'int' and '<null>'.
So, you have to cast the null as well... This works:
int? myint = (testvalue == true) ? 1234 : (int?)null; UPDATE (Oct 2021):
As of C# 9.0 you can use "Target-Typed" conditional expresssions, and the example will now work as c# 9 can pre-determine the result type by evaluating the expression at compile-time.
3 Comments
Ron
Excellent. Solved an issue I was having tonight.
Cirelli94
Ok, this is not strictly the answer to the question but I find it really useful. Anyone know the reason of this behaviour?
Jesse Chisholm
@Cirelli94 The ternary operator
?: tries to deduce the type of the result. It gets int for the first part and null for the second part. It can't implicitly resolve those two. But, when casting the null to be a Nullable<int> (shorthand int?) then the implicit cast of int to int? is found and used for the final assignment.You cannot set an int to null. Use a nullable int (int?) instead:
int? value = null; 
1 Comment
Kasim Husaini
above expression gives "System.InvalidOperationException: Nullable object must have a value." exception.
int does not allow null, use-
int? value = 0 or use
Nullable<int> value 
Comments
public static int? Timesaday { get; set; } = null; OR
public static Nullable<int> Timesaday { get; set; } or
public static int? Timesaday = null; or
public static int? Timesaday or just
public static int? Timesaday { get; set; } static void Main(string[] args) { Console.WriteLine(Timesaday == null); //you also can check using Console.WriteLine(Timesaday.HasValue); Console.ReadKey(); } The null keyword is a literal that represents a null reference, one that does not refer to any object. In programming, nullable types are a feature of the type system of some programming languages which allow the value to be set to the special value NULL instead of the usual possible values of the data type.
https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/null https://en.wikipedia.org/wiki/Null
Comments
Declare you integer variable as nullable eg: int? variable=0; variable=null;
value. For example,Enum.Parse,String.IndexOfand (logically)Dictionary<,>.TryGetValue.