How can I fix the error: System.NullReferenceException: 'Object reference not set to an instance of an object.'

Question

How can I fix the error: System.NullReferenceException: 'Object reference not set to an instance of an object.'

flowerforlife 71

The following is my code:

namespace RegistrationForm  
{  
    public partial class Rent : Form  
    {  
        AptId aptId;  
        Payment payment;  
        public Rent(AptId apt)  
        {  
            InitializeComponent();  
            this.aptId = apt;  
              
        }  
  
        public Rent(Payment pay)  
        {  
            InitializeComponent();  
            this.payment = pay;  
        }  
  
        private void Rent_Load(object sender, EventArgs e)  
        {  
            rentTextBox.Text = aptId.rentTextBox.Text;  
            rentTextBox.Text = payment.rentTextBox.Text;  
        }  
        private void button1_Click(object sender, EventArgs e)  
        {  
            DateTime current = DateTime.Now;  
            MessageBox.Show("Your transaction on " + current.ToString() + " of BHD " + rentTextBox.Text + " was successful!!!");  
  
            this.Close();  
        }  
  
          
    }  
}

I am getting error on this statement: rentTextBox.Text = aptId.rentTextBox.Text;

Error: System.NullReferenceException: 'Object reference not set to an instance of an object.'

Doesn't make sense to me cause the statement under it is the same just a different name and different table referencing name, but it doesn't show any such error.

I would really appreciate if my error is solved in any way.

Thanks in advance

flowerforlife 71 Reputation points

2022-07-28T05:37:36.207+00:00

Thank you very much to all of you for helping me solve the problem. With one of your solutions, the problem now got solved.

God bless you all
Jack J Jun 25,306 Reputation points

2022-07-28T07:04:14.36+00:00

@flowerforlife , Welcome to Microsoft Q&A, I am glad that your problem has been solved. If you have satisfied answer, please click "Accept Answer" and upvote it. It will also help others to solve the similar problem.
Reza Aghaei 4,996 Reputation points Volunteer Moderator

2022-07-28T09:30:13.027+00:00

Cool! As a side-note @flowerforlife : You can accept only one answer which you feel is more useful as an accepted answer for future readers, but you can upvote as many answers which you find useful, including the accepted one.
Krawtch Tun 0 Reputation points

2023-05-10T06:32:37.11+00:00

guys i need to download this one Github Copilot X ?
FARJONA KHATUN 0 Reputation points

2025-01-29T18:02:02.68+00:00

NullReferenceException: Object reference not set to an instance of an object.] AIMES_WEB.StudentPortal.SP_CurrentDues_Sajc.Button1_Click(Object sender, EventArgs e) +3062 System.Web.UI.WebControls.Button.OnClick(EventArgs e) +11596287 System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +273 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1889J

7 answers

Your answer

flowerforlife 71 Reputation points

2022-07-28T05:37:36.207+00:00

Thank you very much to all of you for helping me solve the problem. With one of your solutions, the problem now got solved.

God bless you all
Jack J Jun 25,306 Reputation points

2022-07-28T07:04:14.36+00:00

@flowerforlife , Welcome to Microsoft Q&A, I am glad that your problem has been solved. If you have satisfied answer, please click "Accept Answer" and upvote it. It will also help others to solve the similar problem.
Reza Aghaei 4,996 Reputation points Volunteer Moderator

2022-07-28T09:30:13.027+00:00

Cool! As a side-note @flowerforlife : You can accept only one answer which you feel is more useful as an accepted answer for future readers, but you can upvote as many answers which you find useful, including the accepted one.
Krawtch Tun 0 Reputation points

2023-05-10T06:32:37.11+00:00

guys i need to download this one Github Copilot X ?
FARJONA KHATUN 0 Reputation points

2025-01-29T18:02:02.68+00:00

NullReferenceException: Object reference not set to an instance of an object.] AIMES_WEB.StudentPortal.SP_CurrentDues_Sajc.Button1_Click(Object sender, EventArgs e) +3062 System.Web.UI.WebControls.Button.OnClick(EventArgs e) +11596287 System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +273 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1889J

Answer 1

Rijwan Ansari 766 MVP

Hi @flowerforlife

You can check null value before assigning value as shown:

 rentTextBox.Text = aptId?.rentTextBox?.Text ?? "Null Value";  
 rentTextBox.Text = payment?.rentTextBox?.Text ?? "Null Value";

0 comments

Answer 2

When you have a statement like A.B.C = E.F;, and you receive an NullReferenceException 'Object reference not set to an instance of an object.' on that line of code, it basically means either A, or B or E are null.

To figure out what's wrong there, you can set a breakpoint on the same line, start debugging and then when the breakpoint hits, just check the value of A, B or E.

When NullReferenceException happens?

There are some common cases that you may encounter a NullReferenceException. Here is a summary based on NllReferenceEexception article in .NET documentations. I've put the link of the article in the next section in the answer, where you can find some useful example as well.

A NullReferenceException exception is thrown when you try to access a member on a type whose value is null. A NullReferenceException exception typically reflects developer error and is thrown in the following scenarios:

You've forgotten to instantiate a reference type.
You've forgotten to dimension an array before initializing it.
You get a null return value from a method, and then call a method on the returned type.
You're using an expression to retrieve a value and one of the intermediate values in the expression returns null.
You're enumerating the elements of an array that contains reference types, and an element is null.
A NullReferenceException exception is thrown by a method that is passed null.

Learn more

For more information and examples, take a look at the following links:

NullReferenceException remarks (Microsoft Learn)
What is a NullReferenceException, and how do I fix it? (stackoverflow)
Tutorial: Learn to debug C# code using Visual Studio

Answer 3

Karen Payne MVP 35,606 Volunteer Moderator

Rather than guess, set breakpoints and examine variable values via the debugger. Once known what is causing System.NullReferenceException then figure out how to fix it and/or prevent it in the first place.

It's a great time to get to know breakpoints, working with local window and the debugger in general.
Another option is to place this code into a class than at this point unit test can be written against the code which can do two things, expose issues and tighten up your code overall.

0 comments

Answer 4

Hi,

I believe that the appId or appid.rentTextBox is having null in below method.

 private void Rent_Load(object sender, EventArgs e)  
     {  
         rentTextBox.Text = aptId.rentTextBox.Text;  
         rentTextBox.Text = payment.rentTextBox.Text;  
     }

You can rewrite those by checking null.

 private void Rent_Load(object sender, EventArgs e)  
     {  
         rentTextBox.Text = (aptId.rentTextBox != null) ? aptId.rentTextBox.Text : "Null" ;  
         rentTextBox.Text = (payment.rentTextBox !=null) ? payment.rentTextBox.Text : "Null";  
     }

However, please double check those objects.

Answer 5

Sreeju Nair 12,761

I believe you have null value in any one of the following variables.

rentTextBox
aptId
aptId.rentTextBox

Check the call to the constructor Rent(AptId) and ensure the values are passing correctly. Insert a breakpoint and debug your application.

Hope this helps

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How can I fix the error: System.NullReferenceException: 'Object reference not set to an instance of an object.'

7 answers

When NullReferenceException happens?

Your answer