Ad:

C# Discussion Thread
Unsolved
Views: 16263

Jan 14th, 2009

Object reference not set to an instance of an object.

Expand Post »

Ah man , ive been adjusting the code so much ...

I am trying to make a treeview that display's all the directories and files on theserver (SO FAR SO GOOD) ...

Here's my code to retrieve Directories and files

C# Syntax (Toggle Plain Text)
public string[] GetFileList()
        {
            string[] downloadFiles;
            StringBuilder result = new StringBuilder();
            FtpWebRequest reqFTP;
            try
            {
                reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + txtftpServerName.Text + "/"));
                reqFTP.UseBinary = true;
                reqFTP.Credentials = new NetworkCredential(txtftpUserName.Text, txtftpPassword.Text);
                reqFTP.Method = WebRequestMethods.Ftp.ListDirectory;
                WebResponse response = reqFTP.GetResponse();
                StreamReader reader = new StreamReader(response.GetResponseStream());
 
                string line = reader.ReadLine();
                while (line != null)
                {
                    result.Append(line);
                    result.Append("\n");
                    line = reader.ReadLine();
                }
                result.Remove(result.ToString().LastIndexOf('\n'), 1);
                reader.Close();
                response.Close();
 
                return result.ToString().Split('\n');
            }
            catch (Exception ex)
            {
                System.Windows.Forms.MessageBox.Show(ex.Message);
                downloadFiles = null;
                return downloadFiles;
            }
        }
 
public string[] GetChildFileList()
        {
            string[] downloadFiles;
            StringBuilder result = new StringBuilder();
            FtpWebRequest reqFTP;
            try
            {
                reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + txtftpServerName.Text + "/" + treeView1.SelectedNode.Text + "/"));
                reqFTP.UseBinary = true;
                reqFTP.Credentials = new NetworkCredential(txtftpUserName.Text, txtftpPassword.Text);
                reqFTP.Method = WebRequestMethods.Ftp.ListDirectory;
                WebResponse response = reqFTP.GetResponse();
                StreamReader reader = new StreamReader(response.GetResponseStream());
 
                string line = reader.ReadLine();
                while (line != null)
                {
                    result.Append(line);
                    result.Append("\n");
                    line = reader.ReadLine();
                }
                result.Remove(result.ToString().LastIndexOf('\n'), 1);
                reader.Close();
                response.Close();
 
                return result.ToString().Split('\n');
            }
            catch (Exception ex)
            {
                System.Windows.Forms.MessageBox.Show(ex.Message);
                downloadFiles = null;
                return downloadFiles;
            }
        }
public string[] GetFileList()
        {
            string[] downloadFiles;
            StringBuilder result = new StringBuilder();
            FtpWebRequest reqFTP;
            try
            {
                reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + txtftpServerName.Text + "/"));
                reqFTP.UseBinary = true;
                reqFTP.Credentials = new NetworkCredential(txtftpUserName.Text, txtftpPassword.Text);
                reqFTP.Method = WebRequestMethods.Ftp.ListDirectory;
                WebResponse response = reqFTP.GetResponse();
                StreamReader reader = new StreamReader(response.GetResponseStream());
                
                string line = reader.ReadLine();
                while (line != null)
                {
                    result.Append(line);
                    result.Append("\n");
                    line = reader.ReadLine();
                }
                result.Remove(result.ToString().LastIndexOf('\n'), 1);
                reader.Close();
                response.Close();
                
                return result.ToString().Split('\n');
            }
            catch (Exception ex)
            {
                System.Windows.Forms.MessageBox.Show(ex.Message);
                downloadFiles = null;
                return downloadFiles;
            }
        }

public string[] GetChildFileList()
        {
            string[] downloadFiles;
            StringBuilder result = new StringBuilder();
            FtpWebRequest reqFTP;
            try
            {
                reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + txtftpServerName.Text + "/" + treeView1.SelectedNode.Text + "/"));
                reqFTP.UseBinary = true;
                reqFTP.Credentials = new NetworkCredential(txtftpUserName.Text, txtftpPassword.Text);
                reqFTP.Method = WebRequestMethods.Ftp.ListDirectory;
                WebResponse response = reqFTP.GetResponse();
                StreamReader reader = new StreamReader(response.GetResponseStream());

                string line = reader.ReadLine();
                while (line != null)
                {
                    result.Append(line);
                    result.Append("\n");
                    line = reader.ReadLine();
                }
                result.Remove(result.ToString().LastIndexOf('\n'), 1);
                reader.Close();
                response.Close();

                return result.ToString().Split('\n');
            }
            catch (Exception ex)
            {
                System.Windows.Forms.MessageBox.Show(ex.Message);
                downloadFiles = null;
                return downloadFiles;
            }
        }

This works fine indevidually , but when i try to combine the two:

C# Syntax (Toggle Plain Text)
 
private void btnDoIt_Click(object sender, EventArgs e)
        {
            string[] Parent_Name = GetFileList();
            string[] Child_Name = GetChildFileList();
 
            treeView1.Nodes.Clear();
            if (Parent_Name != null)
            {
                /*          Parent Node             */
                foreach (string filename in Parent_Name)
                {
                    TreeNode ParentNode = new TreeNode(filename);
                    treeView1.Nodes.Add(ParentNode);
 
                    if (Parent_Name != null)
                    {
                        foreach (string filename2 in Child_Name)
                        {
                            TreeNode ChildNode = new TreeNode(filename2);
                            ParentNode.Nodes.Add(ChildNode);
                        }
                    }
                }
            }
        }
private void btnDoIt_Click(object sender, EventArgs e)
        {
            string[] Parent_Name = GetFileList();
            string[] Child_Name = GetChildFileList();

            treeView1.Nodes.Clear();
            if (Parent_Name != null)
            {
                /*          Parent Node             */
                foreach (string filename in Parent_Name)
                {
                    TreeNode ParentNode = new TreeNode(filename);
                    treeView1.Nodes.Add(ParentNode);

                    if (Parent_Name != null)
                    {
                        foreach (string filename2 in Child_Name)
                        {
                            TreeNode ChildNode = new TreeNode(filename2);
                            ParentNode.Nodes.Add(ChildNode);
                        }
                    }
                }
            }
        }

i get an error stating that "Object reference not set to an instance of an object." (LENS ON [foreach (string filename2 in Child_Name)] )

Can anyone maybe give me a clue ?? i dont even know why its complaining because it aught to work...

Happy coding

Last edited by cVz; Jan 14th, 2009 at 10:51 am.

Similar Threads

value of string is cannot conerted into system.array in VB.NET
object reference not set to instance of object+axis2 in Java
Object reference not set to an instance of an object. in VB.NET
Object reference not set to an instance of an object in ASP.NET
How to set attribute to the controls in datagrid? in ASP.NET

cVz

Reputation Points: 29

Solved Threads: 7

Junior Poster

Offline

139 posts
since Mar 2008

Permalink

Jan 14th, 2009

Re: Object reference not set to an instance of an object.

It works with me! but try to debug, that's the one who you can fully trust in.

Ramy Mahrous

Featured Poster

Reputation Points: 480

Solved Threads: 276

Postaholic

Offline

2,189 posts
since Aug 2006

Permalink

Jan 14th, 2009

Re: Object reference not set to an instance of an object.

Its almost certainly correct:

as you go to use Child_name, but you checked parent wasnt null, so child could be

LizR

Reputation Points: 196

Solved Threads: 190

Posting Virtuoso

Offline

1,735 posts
since Aug 2008

Permalink

Jan 14th, 2009

Re: Object reference not set to an instance of an object.

It also works proper with me, but have some thing, that you should look at:
1. You check Parent_Name 2 times. And second one is inside the first one. It looks like question: "Are you really sure that (Parent_Name != null)" ;P

c# Syntax (Toggle Plain Text)
treeView1.Nodes.Clear();
            if (Parent_Name != null)
            {
treeView1.Nodes.Clear();
            if (Parent_Name != null)
            {

and

c# Syntax (Toggle Plain Text)
if (Parent_Name != null)
                    {
                        foreach (string filename2 in Child_Name)
if (Parent_Name != null)
                    {
                        foreach (string filename2 in Child_Name)

2. I suppose you should do that:

c# Syntax (Toggle Plain Text)
treeView1.Nodes.Add(ParentNode);
treeView1.Nodes.Add(ParentNode);

after you fill with data the ChildNode of this ParentNode.

Good luck

Antenka

Reputation Points: 293

Solved Threads: 82

Posting Whiz

Offline

361 posts
since Nov 2008

Permalink

Jan 14th, 2009

Re: Object reference not set to an instance of an object.

Which is what I said in a lot less of a post.

LizR

Reputation Points: 196

Solved Threads: 190

Posting Virtuoso

Offline

1,735 posts
since Aug 2008

Permalink

Jan 14th, 2009

Re: Object reference not set to an instance of an object.

Oh yeah

sorry. First part is your's. Wasn't about to do things like that O.O ... it seems that I need rest a bit ;P

Antenka

Reputation Points: 293

Solved Threads: 82

Posting Whiz

Offline

361 posts
since Nov 2008

Permalink

Jan 15th, 2009

Re: Object reference not set to an instance of an object.

Welll well well, i feel like a retard now hahahahahahahaha!!!

Although , thats not the problem...

The problem lies here

Quote ...

string[] Child_Name = GetChildFileList();

for some reason (i think) the Uri does not change because you have to SELECT a node first...

So i did this

(Toggle Plain Text)

private void btnDoIt_Click(object sender, EventArgs e)
        {
            string[] Parent_Name = GetFileList();
            

            treeView1.Nodes.Clear();
            if (Parent_Name != null)
            {

                /*          Parent Node             */
                foreach (string filename in Parent_Name)
                {
                    TreeNode ParentNode = new TreeNode(filename);
                    
                    // changed the GetChildFileList uri to 'reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + txtftpServerName.Text + "/" + txtShowDirectory.Text + "/"));'

                    txtShowDirectory.Text = filename;

                    string[] Child_Name = GetChildFileList();

                    if (Child_Name != null)
                    {
                        foreach (string filename2 in Child_Name)
                        {
                            TreeNode ChildNode = new TreeNode(filename2);
                            ParentNode.Nodes.Add(ChildNode);
                        }
                    }
                    treeView1.Nodes.Add(ParentNode);
                }
            }
        }

WORKS LIKE A BOMB!!!!!!!!

cept i still get an error on my try -> catch saying

Quote ...

"The remote server returned an error: (550) File unavailable. (eg. File not found, unavailable)."

Obviously there is still some kind of error

cVz

Reputation Points: 29

Solved Threads: 7

Junior Poster

Offline

139 posts
since Mar 2008

Permalink

Jan 15th, 2009

Re: Object reference not set to an instance of an object.

Look i know the problemo is this

Quote ...

string[] Child_Name = GetChildFileList();

if (Child_Name != null)
{
foreach (string filename2 in Child_Name)
{
TreeNode ChildNode = new TreeNode(filename2);
ParentNode.Nodes.Add(ChildNode);
}
}

but i cant really bypass that one or can I ???

cVz

Reputation Points: 29

Solved Threads: 7

Junior Poster

Offline

139 posts
since Mar 2008

Permalink

Jan 15th, 2009

Re: Object reference not set to an instance of an object.

Well if Child_name is null, then look at your function

LizR

Reputation Points: 196

Solved Threads: 190

Posting Virtuoso

Offline

1,735 posts
since Aug 2008

This thread is more than three months old

No one has posted to this discussion for at least three months. Please let old threads die and do not reply to them unless you feel you have something new and valuable to contribute that absolutely must be added to make the discussion complete. Otherwise, please start a new thread in this forum instead.

Previous Thread in C# Forum Timeline: newbie question

Next Thread in C# Forum Timeline: Browse Control in C#

DaniWeb Message

Cancel Changes

User Name
Password