Bee Eee Blog

I ran across an easy way to get wsHttpBinding to work on a remote machine.  This involves just a little bit of code on the client side to complete the authentication.

                VPortalDataServiceClient client = new VPortalDataServiceClient();
                client.ClientCredentials.Windows.ClientCredential.UserName = "btomas";
                client.ClientCredentials.Windows.ClientCredential.Password = "password123";

The UserName is the windows account user name that is hosting the service. This user may just need to be one on the domain that the machine can see — not exactly sure though.  And the Password is the password of that user.

It isn’t straight forward to get a nullable field to serialize. Technically it isn’t supported. But I just discovered a way today. You see null strings are supported. The idea is to ignore the real nullable property while substituting the string version as follows:

    [XmlRoot("Comment")]
    public class Comment
    {
        [XmlIgnore]
        public DateTime? CommentTime { get; set; }

        [XmlAttribute("CommentTime")]
        public string CommentTimeStr
        {
            get
            {
                return (CommentTime.HasValue) ? CommentTime.Value.ToString() : null;
            }

            set
            {
                if (string.IsNullOrEmpty(value))
                    CommentTime = null;
                else
                    CommentTime = DateTime.Parse(value);
            }
        }
  }

Now it can be serialized.

Why there isn’t any reference in the IEqualityComparer documentation to pre-implmented classes that override the function I don’t know.

But here’s one for string comparisons:

StringComparer

This static class contains many different predefined IEqualityComparer instances to be used in functions like “Contains”. Enjoy.

Here is the simple way to get all of the IP addresses for you machine. This code filters out everything but IPv4 address, but to truly get everything just remove the if statement.

string hostName = Dns.GetHostName();
var addrs = Dns.GetHostAddresses(hostName);
bool hasIP = false;
for (int i = 0; i < addrs.Length; i++)
{
    IPAddress addr = addrs[i];
    if (addr.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)
    {
        si.DataIP = addr.ToString();
        hasIP = true;
        break;
    }
}

Here’s the code to set the position of the caret in a richedit control

int position = 12;
richedit1.Select( position, 0 );
richedit1.ScrollToCaret(); // if you want the position to be shown

It’s that simple.

I’ve often been frustrated by the sql that linq produces.  Usually it’s really good, but occasionally it produced monstrosities.   The hard part is getting at the sql that’s produced by a function.  Hovering over the statement in the idea is a real pain so instead I created the following class that dumps the sql to a file

public class DCLogger : IDisposable
    {
        private StringWriter writer;

        public DCLogger(System.Data.Linq.DataContext dc)
        {
            writer = new StringWriter();
            dc.Log = writer;
        }

        #region IDisposable Members

        public void Dispose()
        {
            writer.Flush();
            System.IO.File.WriteAllText( "c:\\temp\\sql.log", writer.ToString() );
        }

        #endregion
    }

To use it just create it passing it you data context. The results are written to the file when it’s disposed.

  using( DCLogger( dc ) )
  {
    // ... some linq statement that executes
  }

There are four different string comparisons for handling string fields with linq to sql.  They are as follows:

The exact macth

DataContext dc = new DataContext(...)
var results =
  from row in dc.table
  where row.string_column == "Exact Match"
  select row;

Begins With:

DataContext dc = new DataContext(...)
var results =
  from row in dc.table
  where row.string_column.StartsWith("Ex")
  select row;

produces an sql match string “Ex%”

Contains

DataContext dc = new DataContext(...)
var results =
  from row in dc.table
  where row.string_column.Contains("Ex")
  select row;

Which is equivalent to “%Ex%”

Ends With

DataContext dc = new DataContext(...)
var results =
  from row in dc.table
  where row.string_column.EndsWith("Ex")
  select row;

Which is equivalent to “%Ex”

I’ve recently been writing an application that builds a linq to sql query dynamically.  For instance:

MyDataContext dc() = new MyDataContext;
var query = dc.MyTables;
query = query.Where( t=>t.id > 10);

and so I want to order it by a certain column:

query = query.OrderBy( t=>t.id )

but the problem is the order direction isn’t know before hand so at first I was stuck with the following:

if ( descending )
    query = query.OrderByDescending( t=>t.id);
else
    query = query.OrderBy(t=>t.id);

Now if there is only a few possible columns to sort against it isn’t too bad.  But when you have 10 different possible columns it really makes a lot of extra work just to control to sort direction.  So I made a little helper class that allows the following.  It works with linq and linq to sql:

query = query.OrderByAscDec( t=>t.id, descending );

here’s the static class that implments the OrderByAscDec function:

static class VPLinqExtensions
{
	public static IOrderedQueryable<TSource> OrderByAscDes<TSource, TKey>(
		this IQueryable<TSource> source,
		System.Linq.Expressions.Expression<Func<TSource,
		TKey>> keySelector, bool IsDescending)
	{
		if (IsDescending)
			return source.OrderByDescending(keySelector);
		else
			return source.OrderBy(keySelector);
	}
}

There doesn’t seem to be much written on blocking socket with c#.  So I’ll write a very short piece, and I’ll only concentrate on client sockets.

Creating a socket is easy here is how:

using System.Net.Sockets;

//...

// Creating a connection
Socket client;
client = new Socket( AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp );
client.Connect(hostName, port);
client.Blocking = false; // This needs to be done after Connect or it will error out.

Here’s how to write data to the socket

// Writing information to the socket
byte[] buffer = ASCIIEncoding.ASCII.GetBytes(messageText);
foreach (byte c in buffer)
{
	SocketError err = SocketError.WouldBlock;
	// need to try again if the socket would have blocked
	while ( err == SocketError.WouldBlock )
	{
		// this version of Send must be used or an exception would be thrown, which I feel is a pain
		// to deal with -- this way you can see handle the error appropriately.
		client.Send(buffer, 0, 1, SocketFlags.None, out err );
	}

	if ( err != SocketError.Success )
	{
		// handle error
		break;
	}
}

And now code to read from a non-blocking socket

// Reading from the socket
// this loop keeps going until there is a socket error or a '0' byte is read which
// in this example marks the end of the message
System.Text.StringBuilder message = new System.Text.StringBuilder();
while ( true )
{
	byte c = 0;
	int bytesRead;
	SocketError err;
	// read a character.
	bytesRead = client.Receive(buffer, 0, 1, SocketFlags.None, out err );
	// checking what happened
	if ( SocketError.Success == err )
	{
		// read a byte!  Let's process it
		if ( bytesRead > 0 )
		{
			// found a null character -- in this case it makes the end of a message.
			if (c == 0)
			{
				// null terminated message received
				break;
			}
			else
				message.Append((char)c);
			}
		}
	}
	else if ( SocketError.WouldBlock != err )
	{
		break;
	}
}

Reading the contents of a web page can be very useful.  Here’s some code I’m developing to read the historical stock prices from http://finance.google.com

string uri = "http://finance.google.com/finance/historical?cid=667226&startdate=Sep+9%2C+2007&enddate=Sep+10%2C+2008&output=csv";
WebRequest request = WebRequest.Create(uri);
WebResponse response = request.GetResponse();
var stream = response.GetResponseStream();
StreamReader reader = new StreamReader(stream, Encoding.GetEncoding("utf-8"));
string page = reader.ReadToEnd();

There you go. Very simple isn’t it? Just got to love .Net