I am developing a autogenerated tax invoice system but upon clicking the submit button this is showing.

Question

1.00/5 (2 votes)

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System.NullReferenceException
  HResult=0x80004003
  Message=Object reference not set to an instance of an object.
  Source=SmartInvoice
  StackTrace:
   at SmartInvoice.Pages.Master.Pages_Master_Index1.<ExecuteAsync>d__9.MoveNext() in C:\Users\LENOVO\source\repos\SmartInvoice\SmartInvoice\Pages\Master\Index1.cshtml:line 39

What I have tried:

CSHTML

  1  @page
  2  @model SmartInvoice.Pages.Master.IndexModel
  3  @{
  4  }
  5  
  6  
  7  <h2>Invoices</h2>
  8  
  9  <form method="post">
 10      <div class="form-group">
 11          <label for="sportsman">Sportsman:</label>
 12          <input type="text" class="form-control" id="sportsman" name="sportsmanAmount">
 13      </div>
 14      <div class="form-group">
 15          <label for="general">General:</label>
 16          <input type="text" class="form-control" id="general" name="generalAmount">
 17      </div>
 18      <div class="form-group">
 19          <label for="temporary">Temporary:</label>
 20          <input type="text" class="form-control" id="temporary" name="temporaryAmount">
 21      </div>
 22      <button type="submit" class="btn btn-primary">Submit</button>
 23  </form>
 24  
 25  <br>
 26  
 27  <h2>List of Invoices</h2>
 28  
 29  <table class="table">
 30      <thead>
 31          <tr>
 32              <th>Sportsman</th>
 33              <th>General</th>
 34              <th>Temporary</th>
 35              <th>Action</th>
 36          </tr>
 37      </thead>
 38      <tbody>
 39          @foreach (var invoice in Model.Invoices)
 40          {
 41              <tr>
 42                  <td>@invoice.Sportsman</td>
 43                  <td>@invoice.General</td>
 44                  <td>@invoice.Temporary</td>
 45                  <td>
 46                      <a class="btn btn-primary btn-sm" href="/Edit?id=@invoice.Id">Edit</a>
 47                      <a class="btn btn-danger btn-sm" href="/Delete?id=@invoice.Id">Delete</a>
 48                  </td>
 49              </tr>
 50          }
 51      </tbody>
 52  </table>

Posted 3-Apr-24 20:57pm

Srijita Bhattacharya

Updated 3-Apr-24 22:27pm

Richard Deeming

v2

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Comments

Richard Deeming 4-Apr-24 4:29am

Based on the line number, Model.Invoices is null - most likely because your form doesn't submit any details that the model binder could use to bind that property.

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Graeme_Grant · Accepted Answer · 2024-04-03T21:08:00

Solution 1

The answer is in the error message "Object reference not set to an instance of an object". Check the model on the server side in the controller by setting a breakpoint on the return statement. Then check the properties for a null value.

Posted 3-Apr-24 21:08pm

Graeme_Grant

OriginalGriff · Accepted Answer · 2024-04-03T21:14:00

To add to what Graeme has said, this is one of the most common problems we get asked, and it's also the one we are least equipped to answer, but you are most equipped to answer yourself.

Let me just explain what the error means: You have tried to use a variable, property, or a method return value but it contains null - which means that there is no instance of a class in the variable.
It's a bit like a pocket: you have a pocket in your shirt, which you use to hold a pen. If you reach into the pocket and find there isn't a pen there, you can't sign your name on a piece of paper - and you will get very funny looks if you try! The empty pocket is giving you a null value (no pen here!) so you can't do anything that you would normally do once you retrieved your pen. Why is it empty? That's the question - it may be that you forgot to pick up your pen when you left the house this morning, or possibly you left the pen in the pocket of yesterday's shirt when you took it off last night.

We can't tell, because we weren't there, and even more importantly, we can't even see your shirt, much less what is in the pocket!

Back to computers, and you have done the same thing, somehow - and we can't see your code, much less run it and find out what contains null when it shouldn't.
But you can - and Visual Studio will help you here. Run your program in the debugger and when it fails, it will show you the line it found the problem on. You can then start looking at the various parts of it to see what value is null and start looking back through your code to find out why. So put a breakpoint at the beginning of the method containing the error line, and run your program from the start again. This time, the debugger will stop before the error, and let you examine what is going on by stepping through the code looking at your values.

But we can't do that - we don't have your code, we don't know how to use it if we did have it, we don't have your data. So try it - and see how much information you can find out!