Contents
What does a runtime throwing a nullreferenceexception mean?
The runtime throwing a NullReferenceException always means the same thing: you are trying to use a reference, and the reference is not initialized (or it was once initialized, but is no longer initialized). This means the reference is null, and you cannot access members (such as methods) through a null reference. The simplest case:
When do you get a nullreferenceexception in C #?
Some common scenarios where the exception can be thrown: If ref1 or ref2 or ref3 is null, then you’ll get a NullReferenceException. If you want to solve the problem, then find out which one is null by rewriting the expression to its simpler equivalent:
What causes an object reference to be null?
Object variables that are uninitialized and hence point to nothing. In this case, if you access members of such objects, it causes a NullReferenceException. The developer is using null intentionally to indicate there is no meaningful value available.
Why do I get an error on null pointer in C #?
Both a null pointer and a null reference in C# are internally represented as the number zero, and so any attempt to dereference it into its corresponding memory storage causes the operating system to produce an error. The .NET runtime then detects this error and turns it into the NullReferenceException.
How to catch system.nullreferenceexception in C #?
Being a plain old C# exception, NullReferenceException can be caught using a try/catch: try { string s = null ; s.ToString (); } catch (NullReferenceException e) { // Do something with e, please. } Running the code above will produce the following error: System.NullReferenceException: Object reference not set to an instance of an object.
How to avoid nullreferenceexception in.net Core 3?
Nullable reference types are a great way to avoid NullReferenceException s, since you are very explicit about where you expect null and where not. To enable not nullable reference types, create a new .NET Core 3 project and add the following to the csproj file:
Is the user name Null in httpcontext.current?
Specifically, in HttpContext.Current.User.Identity.Name, the HttpContext.Current could be null, or the User property could be null, or the Identity property could be null.