DataGird-DataSet-Thread problem

Hi, can anyone guide me throught this:

In my application, I have a global DataSet. I then run
FTP processes in up to 10 simultaneous threads and each
thread calls progress events in the main application.
When a progress event is called, the main application
writes the input to the global DataSet. Occasionally,
the DataSet writes itself to an XML file. This all works
fine. - But you can't see what's going on.

To provide a GUI I have a DataGrid on the form and it's
DataSource property is the relevant table in the global
DataSet. This works automatically - as the threads
report back, the data appears on the datagrid.

But, once in a while, the whole application crashes with
this message:

An unhandled exception of
type 'System.NullReferenceException' occurred in
system.windows.forms.dll

Additional information: Object reference not set to an
instance of an object.

Any ideas?

Hi, can anyone guide me throught this:

In my application, I have a global DataSet. I then run
FTP processes in up to 10 simultaneous threads and each
thread calls progress events in the main application.
When a progress event is called, the main application
writes the input to the global DataSet. Occasionally,
the DataSet writes itself to an XML file. This all works
fine. - But you can't see what's going on.

To provide a GUI I have a DataGrid on the form and it's
DataSource property is the relevant table in the global
DataSet. This works automatically - as the threads
report back, the data appears on the datagrid.

But, once in a while, the whole application crashes with
this message:

An unhandled exception of
type 'System.NullReferenceException' occurred in
system.windows.forms.dll

Additional information: Object reference not set to an
instance of an object.

Any ideas?

-----Original Message-----
Why don't you debug it and find out exactly what line of code gives you thisexception. That will give you some ideas.

"Eric" <er************@onelan.co.uk> wrote in message
news:05****************************@phx.gbl...

Hi, can anyone guide me throught this:

In my application, I have a global DataSet. I then run
FTP processes in up to 10 simultaneous threads and each
thread calls progress events in the main application.
When a progress event is called, the main application
writes the input to the global DataSet. Occasionally,
the DataSet writes itself to an XML file. This all works fine. - But you can't see what's going on.

To provide a GUI I have a DataGrid on the form and it's
DataSource property is the relevant table in the global
DataSet. This works automatically - as the threads
report back, the data appears on the datagrid.

But, once in a while, the whole application crashes with this message:

An unhandled exception of
type 'System.NullReferenceException' occurred in
system.windows.forms.dll

Additional information: Object reference not set to an
instance of an object.

Any ideas?

.

Ummm... sorry, I am a bit out of my depth here, let me
show you code snippets:

public class Form1 : System.Windows.Forms.Form
{
DataSet dsLog=new DataSet("Log");

....

private void InitializeComponent()
{
this.dgUpload = new
System.Windows.Forms.DataGrid();

....

private void Form1_Load(object sender,
System.EventArgs e)
{
dsLog.Tables.Add("Upload");
dsLog.Tables["Upload"].Columns.Add
("File");
dsLog.Tables["Upload"].Columns.Add
("Status");

dgUpload.DataSource=dsLog.Tables
["Upload"];

....
private void RunThreadedFTPs()
{
//The following initiates the threads
string[] row={"","","","",""};
//The following returns the details of
//the next file to upload
row=FilesToFTP.NextDataRow;
Upload up=new Upload();
up.URL=row[0];
up.LocalFile=row[1];
up.RemoteFile=row[2];
up.FTPProgress+=new
Upload.ProgressDelegate(ThreadFTPProgress);
Thread t=new Thread(new ThreadStart
(up.FTPPut));
t.Name=row[1]+"@"+row[0];
t.Start();
}

private void ThreadFTPProgress(string Status)
{
//The following code writes to DataSet
Log(Thread.CurrentThread.Name, Status);
//If the DataGrid is visibile,
//the application may crash

}

.....

public class Upload
{
public delegate void ProgressDelegate(string
Action);
public event ProgressDelegate FTPProgress;

private void ftp1_Progress(object sender,
Dart.PowerTCP.Ftp.FtpProgressEventArgs e)
{
if (e!=null)
{
long FileSize=e.Length;
long Progress=e.Position;
double PercentDone=Convert.ToDouble
(Progress)/Convert.ToDouble(FileSize)*100;
FTPProgress(PercentDone.ToString("##.#"));
}
}

-----Original Message-----
Are your FTP threads using Control.Invoke or

Control.BeginInvoke to communicate with the GUI thread?

"Eric" <er************@onelan.co.uk> wrote in message

news:05****************************@phx.gbl...

Hi, can anyone guide me throught this:

In my application, I have a global DataSet. I then run
FTP processes in up to 10 simultaneous threads and each
thread calls progress events in the main application.
When a progress event is called, the main application
writes the input to the global DataSet. Occasionally,
the DataSet writes itself to an XML file. This all works fine. - But you can't see what's going on.

To provide a GUI I have a DataGrid on the form and it's
DataSource property is the relevant table in the global
DataSet. This works automatically - as the threads
report back, the data appears on the datagrid.

But, once in a while, the whole application crashes with this message:

An unhandled exception of
type 'System.NullReferenceException' occurred in
system.windows.forms.dll

Additional information: Object reference not set to an
instance of an object.

Any ideas?

.