Internet Explorer does not open application/rtf mimetype

Unknown File Type Dialog

I had an odd problem lately where Internet Explorer (IE 7 & 8 ) stopped opening RTF documents served up by our website. The RTF files were served up by a CGI, so they did not have a “rtf” extension on the URL. IE would present a dialog saying that it did not know what the file type was “Unknown File Type”. All the other browsers (Firefox, Safari, etc) worked fine.

On further investigation I found the server was responding with a mime-type of “application/rtf” and it seems IE no longer knows what this is and expects a mime-type of “application/msword”. I found 2 solutions.

1. The best solution, if you control the server, is to change the mime-type of the documents to “application/msword” ().
2. If you can not change the server, then try adding the following registry entry to define the “application/rtf” mime-type

   [HKEY_CLASSES_ROOT\MIME\Database\Content Type\application/rtf]
   "Extension"=".rtf"

Sorting an array in C#

The following code is a simple and quick way to sort and arbitrary array of objects in C#. I like using a delegate in this way as you can pick any attribute or member of the object to sort on at the time you need to perform the sort in the code.

class Customer {
	internal String sName ;
	internal String sAddress ;
} ;

Customer[] customers = new Customer[20] ;
/* Load array ...*/

Array.Sort<Customer>(customers, new Comparison<Customer>(delegate(Customer l, Customer r)
{
	return (l.sName.CompareTo(r.sName));
})) ;

Make sure the array is full, i.e. no null entries, otherwise you will have to check for null values in l and r.

Dynamically creating C# class instances using reflection.

Reflection, the ability for a program to dynamically inspect itself, is possibly one of the most powerful features of modern programming languages like C# and Java. The following is a simple example of how to interrogate the current C# assembly, locate all the classes that are derived from a base class, and then dynamically created and executed an instance of the class.

I wrote this code for a set of tests I wanted to implement. The idea was to make it simple to add new tests to the project by just adding new class derived from the base “Test” class. The program would then automatically find all the tests and run them.

1. First, create the “Test” base class.
   

   abstract class Test {
     protected String m_sName ;
     public String name { get { return (m_sName) ; } }
     protected Test(String sName) { m_sName = sName; }
     abstract public void run() ;
   }

2. Derive the actual tests from the “Test” base class.
   

   class UsersTest : Test {
     public UsersTest() : base("Test user names and passwords") { }
     override public void run() {
       // Test code does here
     }
   }

3. To run the tests, first get the current Assembly, and find all the Types that are “Classes” and are derived from the class “Test”. Once you have the type you need to Dynamically create and instance of it. This method looks for the default constructor (the one with no parameters) and uses that, however, the code could look for any constructor if required. It then calls the contractor to
   create an instance of the class, and finally executes the classes run() method.
   

   Assembly asm = Assembly.GetExecutingAssembly();
   foreach (Type type in asm.GetTypes()) {
     if (type.IsSubclassOf(typeof(Test)) && type.IsClass) {
       ConstructorInfo ci = type.GetConstructor(new Type[] { });
       Test t = (Test)ci.Invoke(new Object[] { }) ;
       Console.Out.WriteLine ("Running Test - " + t.name);
       t.run();
     }
   }

This is a very simple example, and there are other ways to runs tests, but it is easy to see how this design could be extended and used in all sorts of situations.

Loading an SqlDataReader into a DataGridView

This is a simple example of how to load the results from an arbitrary SQL Query, contained in a SqlDataReader, into a DataGridView on a Windows Form (C# Client application). This is an example of a customised view and not an automatically generated one using the AutoGenerateColumns feature and it also demonstrates calling a SQL Server Stored Procedure from C#.

1. Create the DataGridView object e.g. dgvTrials
2. Add the Column names to the DataGridView using Visual Studio. For each of the columns set the DataPropertyName to the column name returned in the SQL query result set.
   
3. Create the SQL Server stored procedure.

   IF OBJECT_ID('sys.sp_getTrialsByUser') IS NOT NULL
    DROP PROCEDURE [sys].sp_getTrialsByUser
   GO
   CREATE PROCEDURE [sys].sp_getTrialsByUser (@username varchar(50)) AS
   select distinct TRIAL_ID, START_DATE, END_DATE, BOOKACRONYM
       from [sys].TRIALS t
   	where t.USERNAME = @username ;

4. Code up the SQL Query using a SqlConnection, SqlCommand and SqlDataReader and load the SqlDataReader results into a DataTable. Then bind the DataTable to the DataGridView.

   using (SqlConnection connection = new SqlConnection(sConnectString))
   {
     connection.Open();
     using (SqlCommand command = connection.CreateCommand())
     {
       command.CommandText = "[sys].sp_getTrialsByUser";
       command.CommandType = CommandType.StoredProcedure;
       command.Parameters.Add("@USERNAME", SqlDbType.VarChar, 50);
       command.Prepare();
       command.Parameters["@USERNAME"].Value = tbUserName.Text;
       SqlDataReader reader = command.ExecuteReader();
       using (reader)
       {
         DataTable table = new DataTable();
         table.Load(reader);
         dgvTrials.DataSource = table;
       }
     }
   }