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Null reference exception could result at runtime


Null reference exception could result at runtime

You've reserved space for your object, but not yet given it a value. As SLaks said, your specific problem is related to how you're calling the method, but without a strong understanding of what Nothing means, it may not correctly address the underlying question Finally. To give it a value, simply use the equals operator. myObject 100 Simple objects, known as primitives, like strings, numbers and characters, have an implied value when they're not defined. For example, integers are assumed to be zero if they have no value. Draft saved draft discarded Sign up or log in Sign up using Google Sign up using Facebook. Sign up using Email and Password. Post as a guest Name Email discard By posting your answer, you agree to the privacy policy and terms of service. You'd see something like this: Dim myObj As Object myObj New Object You can also do it inline: Dim myObj As Object New Object When you try to do that with your PaintEventArgs, you'll see that that's quite impossible. You call. Dim myE as PaintEventArgs. In this statement, you have reserved space in the memory- that is to say, claimed a parking space we talked about earlier. However, it does NOT have a value! PaintEventArgs requires information that's taken from a Windows Form control. That method you've written needs to handle an event. This post is too long as it is, so hopefully someone else can explain events and how they're related to methods. It's empty. The program cannot function properly because you're telling it to perform an action on something that doesn't exist. To fix it, use the New operator. When making new objects, first reserve them in memory (Dim actually stands for "define in memory and then. Basically, each control (textbox, image, or even the picture itself) raises an event every time it "paints" to the screen. You can "handle" that event; or do actions when it occurs, by doing this: Public Sub OnPaint(sender as Object, e as PaintEventArgs) Handles myControl. In your program, when you get a NRE, mouse over each argument in the function and the object that the function is being called from. If any of them claim to have a value of Nothing, there's your problem. OnPaint You are declaring that whenever myControl raises an event for OnPaint, it will call this method, with arguments provided from the control. You cannot simply substitute the required arguments from elsewhere. In order for it to work properly, the event arguments must be passed. I hope this helps. Please let me know if I've been unclear. When you define a variable, using a statement like this, Dim myObject as Integer. you're claiming one or more of the parking spaces in the parking lot. However, all you've done is declare that this spot is yours, but not what goes in it. Your question is broader than your problem. You're asking what a null reference exception is; this question has been answered many times elsewhere. A NRE (NullReferenceException) is referring to a variable that isn't defined at all We can think about memory as being a vast.




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