c# exception

Question

Greetings !

I am working on a project in which i have to transfer a few values between forms,but i get an exception when running the code. I have another forms other than the main form and i am trying to transfer the value which i am reading from the user in a textbox in the main form to a label in the second form.

Could someone point me in the right direction or give me a clue as to how to solve this exception.

The code for the first form (in which i read the data from the user) is as it follows :

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace interform_communication
{
   public partial class Form1 : Form
   {
      // add a delegate
      public delegate void usrUpdateHandler(object sender, usrUpdateEventArgs e);//IdentityUpdateEventArgs
      // add an event of the delegate type
      public event usrUpdateHandler usrUpdated;
      public Form1()
      {
         InitializeComponent();
      }
      private void button1_Click(object sender, EventArgs e)
      {
         Form2 newf = new Form2();
         string sNewUsr=textBox1.Text;
         usrUpdateEventArgs args = new usrUpdateEventArgs(sNewUsr);
         usrUpdated(this,args);//eroare aici(object reference not set to an instance of an object)
         this.Dispose();
         newf.Show();
      }
}
public class usrUpdateEventArgs : System.EventArgs
{
   private string mUser;
   public usrUpdateEventArgs(string sUser)
   {
      this.mUser = sUser;
   }
   public string user
   {
      get
      {
         return mUser;
      }
   }
}
}

And the code for the second form (in which i display the string from the first form) looks like this :

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace interform_communication
{
   public partial class Form2 : Form
   {
      public Form2()
      {
         InitializeComponent();
      }
      private void Form2_Load(object sender, usrUpdateEventArgs e)
      {
         //string txtUser;
         Form1 f=new Form1();
         f.usrUpdated += new Form1.usrUpdateHandler(Form2_Load);
         label1.Text = e.user;
       }
   }
}

These are some screenshots with the design of the project and the exception which i get when i test my code :

1)The exception that i get

2)The first form

3)The second form

The exception appears after i enter text in the textbox in form 1 and press Submit.

Thank you very much for your time !

Vulpes · Answer

Just as a matter of interest what was the error on that line? It worked perfectly when I tried it myself before posting.

Ovidiu Roman · Answer

Thank you very much for your answers and for your time ! However i was able to solve my problem before reading your answers. I have checked them and Vulpesin your answer there is an erroron this line : internal void usrUpdated(object sender usrUpdateEventArgs e) Jignesh Trivedi your answer works ! Thank you very much for your time ! And this is the tutorial on which i relied to complete the taskand which is very well explained : http://www.c-sharpcorner.com/uploadfile/mosessaur/winformsdelegates09042006094826am/winformsdelegates.aspx

Jignesh Trivedi · Answer

hi you can also pass value using constructor or properties. string sNewUsr = textBox1.Text; Form2 newf = new Form2(sNewUsr); newf.Show(); // Form2 string sNewUser = string.Empty; public Form2(string uname) { sNewUser = uname; // do your code here... } hope this will help you.

Vulpes · Answer

Try this: // Form1 private void button1_Click(object sender EventArgs e) { Form2 newf = new Form2(); usrUpdated += newf.usrUpdated; string sNewUsr = textBox1.Text; usrUpdateEventArgs args = new usrUpdateEventArgs(sNewUsr); usrUpdated(this args); newf.Show(); } // Form2 private void Form2_Load(object sender EventArgs e) // back to EventArgs { // nothing in here } // add this handler internal void usrUpdated(object sender usrUpdateEventArgs e) { label1.Text = e.user; }