C# create dynamic List

Article
2013-09-18

Question

_{Wednesday, September 18, 2013 9:17 AM}

Hi i would like to create a dynamic List in C#. my results is not the same everytime sometimes will be 20 results, 30 results, 34 results and etc. But i want to retrieve out the results stored is that possible? Basically my results is not constant i'm retrieving IP address in the subnet out. but I need to store the IP address in a List and retrieve out.

I declare my list on top and initialize where the results is retrieve shown here.

addIP = new List<string>(); addIP.Add(reply.Address.ToString()); < this will generate the results in the while loop till end of the ip address

i retrieve out using

public void retrieveAllIP()

{

for(int i=0;i<addIP.Count();i++)

{

Debug.WriteLine(addIP[i]);

}

but after doing the forloop it will only display the last ip address

All replies (7)

_{Wednesday, September 18, 2013 10:13 AM ✅Answered | 1 vote}

I have gone through the cocde. I think you need declare and creation of the list out side of the loop.

i.e    stop = true;
                    if (listResults.InvokeRequired == true)
                        this.listResults.Invoke((MethodInvoker)delegate()
                        {

ListViewItem item = new ListViewItem();

                            item.Text = reply.Address.ToString();
                          ** addIP = new List<string>();**
                            addIP.Add(reply.Address.ToString());
                            addIP.Add(deviceType);

the above code for list creates new list each time and your old conntens will be over written. hence you will get only last written item. hope this works.

_{Wednesday, September 18, 2013 11:39 AM ✅Answered | 1 vote}

Hi,

If you are calling "DisplayReply(PingReply reply)" method in a loop, then you should declare out side of this method, preferably in class data item delcaration.

_{Wednesday, September 18, 2013 9:30 AM}

Please add the code you use to get the IPs

Also, it seems like you're adding only one address :

addIP = new List<string>(); addIP.Add(reply.Address.ToString()); < this will generate the results in the

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_{Wednesday, September 18, 2013 9:56 AM}

Hi this is the part to ping and get ping resuts.. thanks!

public void PingCompletedCallback(object sender, PingCompletedEventArgs e)
{
try
{
if (e.Cancelled)
{
Debug.WriteLine("Ping Canceled.");

// Let the main thread resume.
// UserToken is the AutoResetEvent object that the main thread
// is waiting for.
((AutoResetEvent)e.UserState).Set();
}

// If an error occurred, display the exception to the user.
if (e.Error != null)
{
Debug.WriteLine("Ping Failed!");
//this will print exception
Debug.WriteLine(e.Error.ToString());

// Let the main thread resume.
((AutoResetEvent)e.UserState).Set();
}
else
{
PingReply reply = e.Reply;

DisplayReply(reply);

// Let the main thread resume.
((AutoResetEvent)e.UserState).Set();

}
}

catch (Exception ex)
{
MessageBox.Show("Exception " + ex.Message);
}
}
public void DisplayReply(PingReply reply)
{
if (reply == null)
return;

//Console.WriteLine("Ping Status: {0}", reply.Status);

else if (reply.Status == IPStatus.Success)
{

stop = true;
if (listResults.InvokeRequired == true)
this.listResults.Invoke((MethodInvoker)delegate()
{

ListViewItem item = new ListViewItem();

item.Text = reply.Address.ToString();
addIP = new List<string>();
addIP.Add(reply.Address.ToString());
addIP.Add(deviceType);

//string[] row1 = { deviceType, temp,};

//Debug.WriteLine(reply.Address.ToString());
//Debug.WriteLine(deviceType);

//listResults.Items.Add(reply.Address.ToString()).SubItems.AddRange(row1);
});

}
}

public long ToInt(string addr)
{
try
{
return (long)(uint)System.Net.IPAddress.NetworkToHostOrder(
(int)System.Net.IPAddress.Parse(addr).Address);
}
catch (Exception x)
{
MessageBox.Show("Empty or Incorrect IP address specify",
"Note",
MessageBoxButtons.OK,
MessageBoxIcon.Exclamation,
MessageBoxDefaultButton.Button1);

return 0;
}

}
public string ToAddr(long address)
{
return System.Net.IPAddress.Parse(address.ToString()).ToString();
}
public void scanLiveHosts(string ipFrom, string ipTo)
{
long from = ToInt(ipFrom);
long to = ToInt(ipTo);

while (from < to)
{
string address = ToAddr(from);
sendAsyncPingPacket(address);
from++;
}

}

_{Wednesday, September 18, 2013 10:16 AM}

I think you're right Ravi, just remove that line and it should work.

_{Wednesday, September 18, 2013 11:28 AM}

Hi Ravi, thanks for the reply. i will try that later on but i have one question. Do you mean i need to create this **addIP = new List<string>(); **outside else if (reply.Status == IPStatus.Success) or outside this method public void DisplayReply(PingReply reply) ? sorry im a newbie in programming! thanks!

_{Wednesday, September 18, 2013 12:16 PM}

ok i will try it later thanks Ravi.

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C# create dynamic List

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