wapSmart:
Good day all. I am working on a project. A billing system and I have stretch it to some extent but recently I am getting this error

NullReferenceException Object reference not set to an instance of an object

I have searched online on how to resolve this but I haven't been able to resolve this with the solutions proffer...

Please, I need your help in getting this resolved

Thenaijaitguy:
From my experience another thing that can cause it if you're mapping two things that do
not match together .

For example insert data with four values into a table that can only take two values.

So share more info about your project.

Thenaijaitguy:
Bro I'm not here to argue just want to help out.

The question you should ask yourself is what is an object?
By then you will realize we are saying the same thing .

The data I used as example is and object. The table you're inserting into is also an object.
So if the two do not match such exception will come up.

I have experience such exception in different project.

I'm only here to learn and help .
Thank you .

Car Ferrari;

MT:
I assumed you are using C#. What that means is you didn't instantiate the object. For instance , let's say you have a class named Car. If you only create the object this way: Car Ferrari {get; set} . This will create object Ferrari but nullreferenceexception error will be thrown because you haven't assigned a value to the object.

Car Ferrari = new Car( );

MT:


There is just ONE way this can happen.

SUPREMOTM:


Ferrari is an OBJECT REFERENCE variable not an OBJECT itself, and Ferrari will be stored on the stack like every other value type (all the primitive types apart from String are value types). Objects are stored on the Heap.

Thenaijaitguy:
Good day @ MT
Good day @supermotm
Is good to know that we have .net expert in the house .

@op
I think the problems might be from your main.cs class, can you show us the main.cs class.

Thenaijaitguy:
Good day @ MT
Good day @supremotm
It's good to know that we have .net expert in the house .

wapSmart:

          using System;
          using System.Windows.Forms;

          namespace Billing_System
          {
              public partial class Main : Form
              {
                  public Main()
                     {
                         InitializeComponent();
                     }

                 private void productToolStripMenuItem_Click(object sender, EventArgs e)
                    {
                     // to open child form mdi(main) form
                     Product p = new Product();
                     p.MdiParent = this;
                     p.Show();
                    }

                 private void newBillToolStripMenuItem_Click(object sender, EventArgs e)
                    {
                     NewBill nb = new NewBill();
                     nb.MdiParent = this;
                     nb.Show();
                    }

                private void viewBillsToolStripMenuItem_Click(object sender, EventArgs e)
                   {
                     ViewBills vb = new ViewBills();
                     vb.MdiParent = this;
                     vb.Show();
                  }


              }
          }

SUPREMOTM:


Whenever you post source code on this forum, format it so it can look organized and readable like this.

To achieve that, select your code (Ctl+A), then click the octothorpe symbol (#) in nairaland's text editor before you click the Submit button.

The code above only tells us that you have 4 forms (at least) and you want to set one of them as an MDI parent form. You want the 3 other forms to display as MDIChildren within the MDIParent form when certain menu items are clicked.

You should know that codes are generated when you set or do not set certain properties from the Properties Window in Visual Studio Design View. Keep troubleshooting and you'll eventually get the solution since you are the only one with complete access to your source code as well as your forms' design.

Don't worry, you'll be the better for it after you successfully detect the cause of the Exception.

wapSmart:


Really appreciate sir.. Will act in accordance

MT:

@supremotm I will look at how you can subscribe to the group.