An Object is an instance of a Class , it is stored some where in memory. A reference is what is used to describe the pointer to the memory location where the Object resides. The message "object reference not set to an instance of an object" means that you are referring to an object the does not exist or was deleted or cleaned up. This would usually be a run-time error .
Reference Types
Variables in .NET are either reference types or value types . Value types are primitives such as integer and boolean or structure. For ex. Boolean variables, when declared, have a default value:
Reference types, when declared, do not have a default value:
If you try to access a member of a class (here MyClass) then you get a System.NullReferenceException. Which is the same as "object reference not set to an instance of an object" . It indicates that you are trying to access member fields, or function types, on an object reference that points to null. That means the reference to an Object which is not initialized. However, the null-reference exception is designed as a valid runtime condition that can be thrown and caught in normal program flow.
Handling NullReferenceException
It's usually better to avoid a NullReferenceException than to handle it after it occurs. To prevent the error, objects that could be null should be tested for null before being used.
Object Reference variable is just like "pointer in C" but not exactly a pointer. A NullReferenceException typically reflects developer error and is thrown in the following scenarios:
- Forgotten to instantiate a reference type.
- Forgotten to dimension an array before initializing it.
- Is thrown by a method that is passed null.
- Get a null return value from a method, then call a method on the returned type.
- Using an expression to retrieve a value and, although checking whether the value is null.
- Enumerating the elements of an array that contains reference types, and attempt to process one of the elements.
Handling an exception can make your code harder to maintain and understand, and can sometimes introduce other bugs. However, there are many situations where handling the error can be useful:
- Your application can ignore objects that are null.
- You can restore the state of your application to a valid state.
- You want to report the exception.
C#8.0 Nullable reference types
C#8.0 introduces nullable reference types and non-nullable reference types. So only nullable reference types must be checked to avoid a NullReferenceException. Since this is a breaking change, it is launched as an opt-in feature.
By Tina | Follow | Last Updated August 04, 2022
What is object reference not set to an instance of an object? How to solve the error of object reference not set to an instance of an object utility? This post from MiniTool will show you the answers.
On This Page :What Is Object Reference Not Set to an Instance of an Object?
Some C#/.Net beginners have reported that they come across the error of object reference no set to an instance of an object. In fact, the object reference not set to an instance of an object is one of the most common errors when developing .NET applications. This infamous and dreaded error message happens when you get a NullReferenceException. This exception is thrown when you try to access a member, such as a method or a property – on a variable that currently holds a null reference.
We have learned that the nullreferenceexception:object reference not set to an instance of an object is caused by a null reference. So, do you know what a null reference is?
A null reference means that it does not point to any object. Null reference errors are responsible for a good percentage of all application bugs. They are usually very simple problems caused by not adding additional logic to ensure that objects have valid values before using them.
So, when you encounter the error of utility object reference not set to an instance of an object, do you know how to fix it? How to avoid this error?
How to Avoid Object Reference Not Set to an Instance of an Object?
Therefore, in this part, we will show you how to avoid object reference not set to an instance of an object. To avoid the issue of object reference not set to an instance of an object, you can take several measures. Now, we will show some of them.
1. Explicitly check for null and ignore null values.
If you expect the reference sometimes to be null, you can check for it being null before accessing instance members.
2. Explicitly check for null and provide a default value.
In order to avoid object reference not set to an instance of an object, you can choose to check for the null and provide a default value.
3. Explicitly check for null from method calls and throw a custom exception.
In this measure, you can choose to throw a custom exception, only to catch it in the calling codes.
4. Use Debug.Assert if a value should never be null, to catch the problem earlier than the exception occurs.
If you have known that a method can be null but it never should be during the development, then you can choose to use the Debug.Assert() to break as soon as possible when it does occur.
5. Take advantage of the null coalescing operator: ?? [C#] or If() [VB].
In order to avoid the error of object reference not set to an instance of an object, you can also choose to take advantage of the null coalescing operator.
6. Take Advantage of Null Context.
In order to avoid the error of utility reference not set to an instance of object, you can choose to use the null context.
Of course, in order to avoid nullreferenceexception:object reference not set to an instance of an object, you can take other measures.
Final Words
To sum up, this post has shown what the error of object reference not set to an instance of an object is and what causes this error. In addition, this post also shows some measures to avoid this error. If you have any different ideas, you can share it in the comment zone.
About The Author
Position: Columnist
Tina is a technology enthusiast and joined MiniTool in 2018. As an editor of MiniTool, she is keeping on sharing computer tips and providing reliable solutions, especially specializing in Windows and files backup and restore. Besides, she is expanding her knowledge and skills in data recovery, disk space optimizations, etc.
On her spare time, Tina likes to watch movies, go shopping or chat with friends and enjoy her life.