SqlConnection dbcon = new SqlConnection();
dbcon.ConnectionString="Server=(local);database=jgtest;Integrated Security=SSPI";

Basically the Server=(local) may not work with a named instance or with DNS issues. For named instances use the IP address\instance_name. eg I have a sqlserver instance called JPGPRIV, so the server element of the connection string is:

Server=192.168.0.5\JPGPRIV

String query = "SELECT id, description from CONSource";
DBCONSource dset = new DBCONSource();
SqlDataAdapter da = new SqlDataAdapter(query, dbcon);
da.Fill(dset,0,5,"CONSource");
dbcon.Close();

for (int cnt=0; cnt<10; cnt++) {
  DataTable tab = dset.CONSource;
  dset.CONSource.AddCONSourceRow("example"+cnt);
}

da = new SqlDataAdapter(query, dbcon);
// Now, to set the commands
SqlCommandBuilder bld = new SqlCommandBuilder(da);
da.InsertCommand = bld.GetInsertCommand();
da.UpdateCommand = bld.GetUpdateCommand();
da.DeleteCommand = bld.GetDeleteCommand();
// note it needs the table name within the db to do the mapping
da.Update(dset, "CONSource"); 
dbcon.Close();
dset.AcceptChanges();

In the data source set seed as 0, increment as -1, and readonly to false for the autoinc column. This allows the local dataset to assign decreasing negative keys, while the server assigns increasing positive keys.

da.RowUpdated += new SqlRowUpdatedEventHandler(OnRowUpdated);
// note it needs the table name within the db to do the mapping
da.Update(dset, "CONSource"); 
...

protected static void OnRowUpdated(object sender, SqlRowUpdatedEventArgs args) {
  if (args.StatementType == StatementType.Insert) {
    SqlConnection con = args.Command.Connection;
    Object new_id = 0;

    // sqlserver 2000 version
    SqlCommand id_cmd = new SqlCommand("select scope_identity() as id",          con);
    new_id = id_cmd.ExecuteScalar();
    if (new_id== System.DBNull.Value) {
      // sqlserver earlier version
      id_cmd = new SqlCommand("select @@IDENTITY", con);
      new_id = id_cmd.ExecuteScalar();
      if (new_id== System.DBNull.Value) {
        throw new Exception("Why doesn't it work??!!");
      }
    }
    // Retrieve the identity value and store it in the id column.
    args.Row["id"] = new_id;
  }
} // end of onRowUpdated
       

DataTable tab = dset2.Tables["CONSource"]; 
tab.Columns.Add("id",System.Type.GetType("System.Int32"));
tab.Columns.Add("description", System.Type.GetType("System.String"));

for (int cnt=0; cnt<3; cnt++) {
  DataRow anyRow = dset2.Tables["CONSource"].NewRow();
  anyRow["id"] = -1;  
  anyRow["description"] = "example";
  dset2.Tables["CONSource"].Rows.Add(anyRow);
}
       

  anyRow["description"] = DBNull.Value;

Testing nulls

if (new_id== System.DBNull.Value) {

con.Open();
SqlTransaction my_trans = con.BeginTransaction();
da1.InsertCommand.Transaction=my_trans;
da2.InsertCommand.Transaction=my_trans;
try {
  da1.Update(dset1, "CONSource");
  da2.Update(dset2, "CONSource");
  my_trans.Commit();
} catch (SqlException ex) {
  try {
    my_trans.Rollback();
  } catch (SqlException ex1) {
    if (my_trans.Connection != null) {
      Console.WriteLine("An exception of type " + ex1.GetType() +
         " was encountered while attempting to roll back the transaction.");
    }
  }
  Console.WriteLine(ex.ToString());
  Console.WriteLine("Update failed.");
}
con.Close();

Now Guid's are nasty, for various reasons, but if you go for them then use the System.Guid class member NewGuid().

Guid val = Guid.NewGuid();

try {
  String query = "select id,desc from a_table";
  SqlConnection con = new SqlConnection();
  con.ConnectionString="Server=(local);database=jgtest;Integrated Security=SSPI";
  con.Open();
  SqlCommand cmd = new SqlCommand(query,con);
  SqlDataReader reader =cmd.ExecuteReader();
  while (reader.Read()) {
    int id = reader.GetInt(0);
    String desc = reader.GetString(1);
  }
  reader.Close();
  con.Close();
  return ret;
} catch (Exception ex) {
  System.Console.WriteLine(ex.Source);
  return ret;
}

TCPListener server = new TCPListener( 23 ); 
server.Start();
Socket accept = server.Accept();

try {
  IPAddress ipAd = IPAddress.Parse("172.21.5.99");
  TcpListener myList=new TcpListener(ipAd,8001);
  myList.Start();
         
  Socket s=myList.AcceptSocket();
  Console.WriteLine("Connection accepted from "+s.RemoteEndPoint);
         
  byte[] b=new byte[100];
  int k=s.Receive(b);
  for (int i=0;i<k;i++)
    Console.Write(Convert.ToChar(b[i]));
  ASCIIEncoding asen=new ASCIIEncoding();
  s.Send(asen.GetBytes("The string was recieved by the server."));
  s.Close();
  myList.Stop();
} catch (Exception e) {
  Console.WriteLine("Error..... " + e.StackTrace);
} 

IPHostEntry ipHostInfo = Dns.Resolve(host);
IPAddress ipAddress = ipHostInfo.AddressList[0];
IPEndPoint remoteEP = new IPEndPoint(ipAddress, port);
serverSoc_ = new Socket(AddressFamily.InterNetwork,SocketType.Stream,ProtocolType.Tcp);
serverSoc_.Connect(remoteEP);

TCPClient telnet = new TCPClient( "telnet.host.com", 23 );
Stream telnetStream = telnet.GetStream();
StreamWriter output = new StreamWriter( telnetStream );
StreamReader input = new StreamReader( telnetStream );

WebRequest request = WebRequestFactory.Create( = "http://to.post.to.com"    );
Stream input = request.GetResponse().GetResponseStream();
... read stuff from input ...
input.Close();

Error codes from SocketException

No code here, but a .Net horror. All the socket exception thrown include a useless error number which is thrown by the underlying winsock libs. A quick search found a german firewall site which allowed me to work out what the errors actually were. Follow the link for the information - you don't have to read german.

Find Disk Size

public static void getDiskSize(String drive, 
  out ulong o_size, out ulong o_used, out ulong o_avail) {
  // Check the drive exists
  if (!Directory.Exists(drive+@":\")) 
        throw new DirectoryNotFoundException("No drive info");

  ManagementObject disk = new
  ManagementObject("Win32_LogicalDisk.DeviceID=\""+drive+":\"");

  UInt64 freespace = (UInt64)disk.Properties["FreeSpace"].Value ;
  UInt64 size = (UInt64)disk.Properties["Size"].Value ;

  Console.WriteLine("Harddisk size: "+ size);
  Console.WriteLine("Bytes used: "+ (size - freespace));
  Console.WriteLine("Bytes availlable: "+ freespace);
  o_size = size;
  o_used= ((size - freespace));
  o_avail = freespace;
}

String str = Encoding.ASCII.GetString(buff,0,buff.Length);

byte [] end_ln = Encoding.ASCII.GetBytes("\r\n");

try {
  String k = headers_.Get(HEAD_CONTENTLENGTH);
  int ret = Int32.Parse(k);
  return ret;
} catch (FormatException) {
  // TODO:
}
or
System.Convert.ToInt32(some_string);

String [] lines = hdr_str.Split('\n', '\r'); 
int cnt=0;
foreach (String line in lines) {
  if (line==String.Empty) continue;
   ... stuff...
}

DateTime.Now;

Enum

public enum RESPONSE_CODES : int {
  OK = 200,
  BadRequest = 400,
  InternalServerError = 500,
};

public void Go(string drive) {
  running_ = true;
  // Note the use of the delegate here.
  myTh_ = new Thread(new ThreadStart(this.Run));
  // Starting the thread invokes the ThreadStart delegate.
  myTh_.Start();
}

public void Stop() {
  if (myTh_!=null) {
    running_ = false;
    myTh_.Abort();

    myTh_=null;
  }

}

private void Run() {
  try {
    while (running_) {
	 ... do stuff ...
    }
  } catch (ThreadAbortException ) {
    // TODO:
  }
}