You Cannot Call A Method On A Null Valued Expression

Hey there

Have you ever tried to call a method on a null valued expression? If so you know that it’s not a pleasant experience. You get an error message like “Object reference not set to an instance of an object” and you’re left scratching your head wondering what it all means.

What is a Null Valued Expression?

Simply put a null valued expression is an expression that has no value. It’s like a variable that has been declared but not assigned a value. It’s an empty space in your code and it can cause some issues if you try to call a method on it.

To help you better understand here’s a useful table of information:

Understanding the Error Message

Don’t you just hate it when your computer won’t listen to your commands? That’s the feeling you get when you get the dreaded “You cannot call a method on a null valued expression” error. If you’re anything like me this message usually makes you want to throw your laptop out the window – never a good idea!

But don’t worry this error isn’t as complicated as you think. The error simply means that you’re trying to call a method on a null valued object. A null object is an object with no value. So when you try to call a method on that object you’re essentially trying to get something out of nothing which – as you may have guessed – isn’t possible. Once you know what the error message means you can start to figure out how to fix it.

An easy way to resolve this error is to check the code for the object you’re trying to call the method on. Make sure that the object is not set to null. If it is you’ll have to set the object to a value before you can move further.

Another common reason for this error is that a variable has been declared but not initialized. Make sure that every variable has been constructed with an initial value; if not it will be null and you won’t be able to call a method on it.

So there you have it; a brief breakdown of the “You cannot call a method on a null valued expression” error. Now that you know what it means you can get on with debugging your code and achieving coding glory!

Troubleshooting

So you’re stuck and you have no idea what to do to fix that pesky “You cannot call a method on a null valued expression” error? Don’t worry you’re not alone. In this portion of our article we’ll provide a few tips to help you identify and troubleshoot this error.

First try restarting the program. Don’t underestimate the power of a good ol’ restart. It can do wonders for the system and will often resolve stubborn errors.

If that doesn’t work examine the code for any typos or syntax errors you may have missed. An extra comma a misplaced letter – it might look minor but it can cause major problems. Double check your code indentation and variable names. Sometimes it’s the small things that count.

Ensure your variables are initialized and objects fully instantiated before attempting to call their methods. If they are null your code will not run – hence the error. Verify your variables and objects and be sure they are set to their intended values.

Lastly if you are unable to identify the problem try caching the application or restarting the server. Caching can help improve program performance but it can strain the system in the process. Restarting the server can help clear any bad cache that may be causing the error.

If these steps still don’t help it’s probably time to ask for assistance from an experienced programmer.

Workaround Solutions

When you try to call a method on a null valued expression the inevitable happens: you get an error thrown your way. It’s a real bummer indeed! But have no fear there are a couple of workarounds you can consider as solutions depending on what’s going on with your code.

The first and often the simplest workaround is to simply check if the expression is null or not. You could do this using an If statement to make sure the call won’t be made if the expression is null. This solution is really handy when your code is expecting the expression to sometimes be null (or at the least you know that it won’t be null every single time).

Another workaround is to use a Null-coalescing operator and optionally provide another value to use in the expression if it’s null. This way if your expression is null for some reason that alternative value will be used instead. It’s a great solution if you’re not too sure what’s causing the null value.

Finally if you’re still having trouble with the issue it may be worth checking whether the expression setting that value might be wrong or not. You could change it to use another method and see if that resolves the issue or not. Usually this kind of trial and error process enough to locate the source of the problem and resolve it quickly.

So as a recap if you’re trying to call a method on a null valued expression and get an error the key is to simply check if the expression is null use a Null-coalescing operator or check if the expression setting the value is correct. All these solutions can help you to sidestep the issue so you can move on with your code.

Resources

• https://www.sdcc.bnl.gov/phobos/Detectors/Computing/Orant/doc/appdev.804/a58241/ch7.htm