How do I solve this issue

Question

0.00/5 (No votes)

See more:

System.NullReferenceException
  HResult=0x80004003
  Message=Object reference not set to an instance of an object.
  Source=Assistant_Accountant_V1.0
  StackTrace:
   at Assistant_Accountant_V1._0.General.ApplicationSetting.ConnectionString() in E:\C# Project\Assistant_Accountant_V1.0\Assistant_Accountant_V1.0\General\ApplicationSetting.cs:line 13
   at Assistant_Accountant_V1._0.LoginForm.LoginButton_Click(Object sender, EventArgs e) in E:\C# Project\Assistant_Accountant_V1.0\Assistant_Accountant_V1.0\Screens\LoginForm.cs:line 30
   at System.Windows.Forms.Control.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
   at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ButtonBase.WndProc(Message& m)
   at System.Windows.Forms.Button.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
   at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   at Assistant_Accountant_V1._0.Program.Main() in E:\C# Project\Assistant_Accountant_V1.0\Assistant_Accountant_V1.0\Program.cs:line 18

What I have tried:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Configuration;

namespace Assistant_Accountant_V1._0.General
{
public class ApplicationSetting
{
public static string ConnectionString()
{
return ConfigurationManager.ConnectionStrings["rbx"].ConnectionString;
}

}
}

Posted 28-Jun-19 13:01pm

zakir7dipu

Updated 1-Jul-19 4:00am

Add a Solution

3 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

MadMyche · Answer 1 · 2019-06-28T14:04:00

Solution 1

Check for null

C#

public static string ConnectionString()
{
  var cs = ConfigurationManager.ConnectionStrings["rbx"].ConnectionString;
  if (cs != null) { return cs.ToString(); }
  else { throw new Exception("Connection string not found"); }
}

Posted 28-Jun-19 14:04pm

MadMyche

Updated 1-Jul-19 3:35am

v2

Comments

zakir7dipu 29-Jun-19 11:20am

In the app.config file I do <add name="rbx" connectionstring="">
and then In the ApplicationSetting class I writ the previous code. But when I run that program in the debugger at VS It shows the error on This line "return ConfigurationManager.ConnectionStrings["rbx"].ConnectionString;". now what will your solution. And your given answer also is not working. and showing the same ERROR

MadMyche 1-Jul-19 9:34am

Try the "Improve Question" widget and edit your question to also include your app.config file...
I did notice I had a typo in my answer; missed the semi-colon key. Has been updated

OriginalGriff · Answer 2 · 2019-06-28T18:54:00

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 yesterdays 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, VS 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, VS will stop before the error, and let you examine what is going on by stepping through the code looking at your values.

In this case it's almost certainly that ConfigurationManager.ConnectionStrings["rbx"] is returning null to indicate that there is no string called "rbx" in the store, so you will need to find out why. If may be that you never added one, it may be that you spelled it wrong - we can't tell from here!

W∴ Balboos, *GHB* · Answer 3 · 2019-07-01T04:00:00

From the last line of your included code - the beginning (often) of the error that propagates through all those other references:

at Assistant_Accountant_V1._0.Program.Main() in E:\C# Project\Assistant_Accountant_V1.0\Assistant_Accountant_V1.0\Program.cs:line 18

This reference may well show you what has the problem at runtime. Did you give this a look?

How do I solve this issue

3 solutions

Solution 1

Solution 2

Solution 3

Add your solution here

Preview 0