object reference cannot set to the instance of object?

Question

I have one method called Appendtxtdata(string value). in form1.cs and i want to use it in another class abc.cs for write text. i used following code but doesnt work. Thanku. in form1.cs. public void AppendTxtdata(string value) { try { if (InvokeRequired) { this.Invoke(new Action (AppendTxtdata) new object[] { value }); return; } txtdata.Text += value; } catch { } } in abc.cs public void getdata() // to run server // { Form1 f = new Form1(); f.AppendTxtdata(data sent); } the getdata method calling in another method and that method is called in form1 in thread.

Member1 · Answer

I attached error snap here

Raja T · Answer

What is error your getting ?

Member1 · Answer

Yes file created and but giving error file is in another process because see below code . public void AppendTxtdata(string myval) { try { if(InvokeRequired) { this.Invoke(new Action (AppendTxtdata) new object[] { myval }); return; } Globalvariable.SomeData += myval; string t = Globalvariable.SomeData; StreamWriter sw = new StreamWriter(@C:\Users\Priya\Desktop	est.txt); sw.Write(t); } catch { } StreamReader sr = new StreamReader(@C:\Users\Priya\Desktop	est.txt); txtdata.Text += sr.ReadToEnd(); } error file attached here

Raja T · Answer

Hi Which one is not working? which thread is problem? Please describe? Are you working on write logfile as my sugguestion?

Member1 · Answer

This is not working sir problem is in thread. now the situation is when i close restart client server also restarted. before edit this wasnt happen.

Member1 · Answer

This is not working sir problem is in thread.

Raja T · Answer

Hi Yes.It is my sugguestion only you can try other option if you can possible.

Member1 · Answer

You mean the data which have to display on textbox will firstly save in txtfile nd then read txtfile onto textbox.but do it complicates the procedure

Raja T · Answer

Okay. I will give one sugguestion why are showing every time data showing in textbot i dnt know instead of showing textbox you can write log file (means create one text file write response data to textfile) finally read the data from text file and display data in textbox.

Raja T · Answer

Hi thanks for the appreciation :)

Raja T · Answer

Hi I am not sure why data not shows at runtime.

Member1 · Answer

I think this is last step  Your answers help me alot to solve issue. thanks

Member1 · Answer

This concept of globalvariable class is working but data not shows at runtime it shows when i close tcpclient object and tcplistener object. why this happend? here is the code for button  when i clicked this stop button data shows in txtbox. private void button1_Click(object sender EventArgs e) { try { AppendTxtdata(Environment.NewLine +Data sent to Client :  + clientSocket.Client.RemoteEndPoint + Environment.NewLine); this.clientSocket.Close(); this.serverSocket.Stop(); } catch { } }

Raja T · Answer

Hi Try this Create new class like global variable using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace DemoWindowsFormsApplication { class Globalvariable { public static string SomeData = ; } } Form1.cs ----------- public void AppendTxtdata(string value) { try { Globalvariable.SomeData += I am from form 1 
 ; if (InvokeRequired) { this.Invoke(new Action (AppendTxtdata) new object[] { value }); return; } Globalvariable.SomeData += value; } catch { } textBox1.Text = Globalvariable.SomeData; MessageBox.Show(textBox1.Text); } form2.cs ------------ public void getdata() // to run server // { //Globalvariable.SomeData += I am From Second form; aaa a = new aaa(); a.AppendTxtdata(I am calling form2 ); }

Member1 · Answer

Can you show me sample code regards with my code i tried assigning value to textbox but it doesnt show anything

Raja T · Answer

Okayso try like you can delcare one global variable and assingn the data to global variable in form1. After that finally textbox value assign to global variable data like txtbox.text =globalvariable; Now call form 2 assign values to global variable only. After that finally textbox value assign to global variable data like txtbox.text =globalvariable;

Member1 · Answer

full data want to show on 1 form at a time if method runs in another class form 1 close and 2 opens but all data from form1 also need to appear on form2.

Raja T · Answer

In my understandingEvery time call the method AppendTxtdata(string value). you want display data in textbox when condition false that time only hide the form1 right?

Raja T · Answer

you want call belllow method public void AppendTxtdata(string value) { try { if (InvokeRequired) { this.Invoke(new Action (AppendTxtdata) new object[] { value }); return; } txtdata.Text += value; } catch { } } you need display in form2 ?

Member1 · Answer

I cant do that I have to write data to same textbox on form 1. In my method the InvokeRequired gets false when method called from handleClient class.

Raja T · Answer

For Example first form like ------------------- 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 WindowsFormsApplication1 { public partial class Form2 : Form { public Form2() { InitializeComponent(); } private void Form2_Load(object sender EventArgs e) { //txtdata.Text = Welcome; } public void AppendTxtdata(string value) { try { if (InvokeRequired) { this.Invoke(new Action (AppendTxtdata) new object[] { value }); return; } txtdata.Text += value; MessageBox.Show(txtdata.Text); } catch { } } } } 2nd form ------------------ 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 WindowsFormsApplication1 { public partial class abc : Form { public abc() { InitializeComponent(); } private void abc_Load(object sender EventArgs e) { getdata(); } public void getdata() // to run server // { Form2 f = new Form2(); f.AppendTxtdata(I am from form abc); f.ShowDialog(); this.Close(); } } }

Raja T · Answer

Hi You need display the textbox data in 2nd form. So you can are you calling like bellow public void getdata() // to run server // { Form1 f = new Form1(); f.AppendTxtdata(data sent); } just change like below public void getdata() // to run server // { Form1 f = new Form1(); f.AppendTxtdata(data sent); f.ShowDialog(); }

Member1 · Answer

I sent my code actually this is not exact one code but its just a type of code i have . Please help me im stuck here.

Raja T · Answer

Hi Please send code/screenshot of the both form .cs i will check you. why are you getting error. I have created two forms. one form conatins method definition like in form1.cs. public void AppendTxtdata(string value) { try { if (InvokeRequired) { this.Invoke(new Action (AppendTxtdata) new object[] { value }); return; } txtdata.Text += value; } catch { } } Second form calling the function like in abc.cs public void getdata() // to run server // { Form1 f = new Form1(); f.AppendTxtdata(data sent); } I am not getting error above mentioned code. Thanks

Member1 · Answer

I am trying to write code for multiple client server and it is working . But I want to display data conversation on textbox for that I have following method in form1.cs which if calling from same class this runs but when calling from another class handleClient.cs this doesnt works and giving object reference not set to an instance : null reference exception error but when I putted breakpoint there it shows data in loop but break just after the loop and doesn't displays data. If i create instance of form1 like this Form1 f = new Form1 it doexnt give null reference error but also data not printed in textbox. one more error I got i.e.unreachable code detected after while loop in form1.cs I attched my code here please have llok once.

Raja T · Answer

Hi Please explain what you want briefly about your requirement so i will help you buddy.

Member1 · Answer

messagebox shows data which supposed to display in text box but then why cant it just print in text box

Raja T · Answer

Hi If you getting same error please checkout below url http://stackoverflow.com/questions/8206810/object-reference-not-set-to-an-instance-of-an-object

Raja T · Answer

Hi I have checked your code it is working fine in my end. I am not getting any error. Try this bellow like message box using in form1.cs public void AppendTxtdata(string value) { try { if (InvokeRequired) { this.Invoke(new Action (AppendTxtdata) new object[] { value }); return; } txtdata.Text += value; MessageBox.Show(txtdata.Text); } catch { } } now you can call abc.cs file pass the paramtr it will call form1.cs and message is will displayed. Thanks