unresolved hashtable problem [modified]

Jassim Rahma

I a trying to have a hashtable class to populate all the variables from my database to be saved and used in my application as public variables. this is my public class

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;

namespace cure_hospital_management
{
class public_class
{
public Hashtable _sysem_parameters_hash;

    public void get\_system\_parameters()
    {
        \_sysem\_parameters\_hash = new Hashtable();
        \_sysem\_parameters\_hash.Add("Name", "Jassim Rahma");
    }
}

}

In my MainFom_Load I am calling:

public_var.get_system_parameters();
public_var._sysem_parameters_hash.Add("Age", "36");

then I am trying to read the hashtable value like this:

MessageBox.Show(public_var._sysem_parameters_hash("Name").ToString());

but getting this error on the reading line (the MessageBox): System.NullReferenceException was unhandled by user code Message="Object reference not set to an instance of an object." Source="cure" StackTrace: at cure_hospital_management.frmDoctorDashboard.frmDoctorDashboard_Load(Object sender, EventArgs e) in C:\Users\Jassim\Documents\Visual Studio 2008\Projects\Cure\Cure\doctor_dashboard.cs:line 2050 at System.EventHandler.Invoke(Object sender, EventArgs e) at System.Windows.Forms.Form.OnLoad(EventArgs e) at System.Windows.Forms.Form.OnCreateControl() at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible) at System.Windows.Forms.Control.CreateControl() at System.Windows.Forms.Control.WmShowWindow(Message& m) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.ScrollableControl.WndProc(Message& m) at System.Windows.Forms.ContainerControl.WndProc(Message& m) at System.Windows.Forms.Form.WmShowWindow(Message& m) at System.Windows.Forms.Form.WndProc(Message& m) at DevExpress.XtraEditors.XtraForm.WndProc(Message& msg) at cure_hospital_management.frmDoctorDashboard.WndProc(Message& m) in C:\Users\Jassim\Documents\Visual Studio 2008\Projects\Cure\Cure\doctor_dashboard.cs:line 84 at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.DebuggableCallback(In

Luc Pattyn

Done too much VB coding?

MessageBox.Show(public_var._sysem_parameters_hash["Name"].ToString());

FYI: instead of Hashtable, use Dictionary<string, string> and you get rid of all those (string) castings and ToString() conversions. :)

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Som Shekhar

jrahma wrote:

unresolved hashtable problem

Are't all problems unresolved? once they are resolved, they become references ;)

Jassim Rahma

this is the up-to-date statu:! Unresolved hashtable problem[^]

Som Shekhar

Ok. I went through the whole thing. So far, someone else hasn't been able to repeat your error. Everytime, binarycoder is answering your specific questions that you ask. Could you post your complete code that shows error? If it shows error then it can be solved. May be some mistake is happening somewhere.

Jassim Rahma

The full code is already uploaded at sky drive as mentioned in my MSDN forum thread public_class.cs[^] main_form.cs[^] doctor_dashboard.cs[^]

Som Shekhar

Hi jrahma, I cannot compile this code for obvious reasons coz there are so many links in it. Can't you strip down this code to bare minimum and see just post the problem area? Basically public_class with minimum requirements and two basic forms with calling public_class? if the problem doesn't happen in that form, it is not a problem related to hashtable. Som

Jassim Rahma

as I have mentioned in my MSDN thread, I have no problme compiling the code because no errors dring the build. The error pops up a run time. I als don't have problem when moving the line: MessageBox.Show(public_var._sysem_parameters_hash("Name").ToString()); to main_form.cs

Som Shekhar

What I understood from the complete QA is that you face an error when you access a member of hashtable. I cannot go through each line of your code to identify where the problem happens till the time i cannot compile the complete code. If you can provide a stripped down version of three cs files which i can compile and find the error during run time, i could help. You could otherwise try to add a breakpoint just before the line where error happens and look into contents of hashtable. may be you can write a method to do just this. The following method will show the contents of the hashtable in the output window. When you see the error in the messagebox line, u can see if the content is available in the hashtable or not.

private void PostDataIntoDebug(Hashtable _sysem_parameters_hash)
{
#if DEBUG
foreach (var a in _sysem_parameters_hash.Keys)
{
Debug.WriteLine(string.Format("{0} - {1}", a, _sysem_parameters_hash[a]));
}
#endif
}

Jassim Rahma

I am getting: Object reference not set to an instance of an object. on this line:

foreach (var a in public_var._sysem_parameters_hash.Keys)

from your code... you might say because hashtable is not initilized or somkething similar.. but why? that's my question... Thanks...

Som Shekhar

jrahma wrote:

you might say because hashtable is not initilized or somkething similar.. but why? that's my question...

Well, this is the answer not the question. You need to go through your code step by step and find out where the hashtable was initialized. I went through the complete discussion once again on MSDN. What i understand is that you are utilizing the same hashtable from different forms but you are initializing them separately. I suggest making a small change of making the class and variable static and see if this solves your purpose:

static class public_class
{
public static Hashtable _sysem_parameters_hash;

    public static void get\_system\_parameters()
    {
        \_sysem\_parameters\_hash = new Hashtable();
        \_sysem\_parameters\_hash.Add("Name", "Jassim Rahma");
    }
}

Jassim Rahma

Now I cleaned the whole application an created a new application just for the hashtable issue and I am still getting the same error. Hashtable project The above file has a hastable project with three files.. public_class.cs, Form1.cs and Form2.cs, you can see that no issue reading the value in Form1 load but when you click on Form2 it will throw the error... it's seems the hashtable was no initilized but i don't know what to do to fix this in Form2...

modified on Monday, April 26, 2010 9:54 AM

Som Shekhar · modified on Monday, April 26, 2010 9:54 AM

Well it was easy to catch. Thanks for the effort of stripping it down. Just change

Form2 myForm = new Form2();

to

Form2 myForm = new Form2(public_var);

and it works. You created the Constructor but didn't use it.

Jassim Rahma

Problem solved :) Thanks Som.... Thanks everyone...

Som Shekhar

:) Cool.