Th30z - Coding on the Fly » C#

C# Oracle for Beginners

Matteo Bertozzi — Sat, 25 Apr 2009 05:22:26 +0000

In the last two days, at work I had a couple of hours to play with Oracle.
I’ve made a simple class to Wrap the .NET OracleConnection and here there’s a simple example with Connection/Disconnection a couple of CREATE TABLE, INSERT a STORED PROCEDURE and a FUNCTION a couple of SELECT to show JOIN and other operations.


OracleDatabase db = new OracleDatabase();
db.Connect("192.168.3.2", "system", "password");

// Create And Populate Tables
db.ExecuteNonQuery("CREATE TABLE tb1 (a NUMBER NOT NULL, b CHAR(20))");
db.ExecuteNonQuery("INSERT INTO tb1 (a, b) VALUES (10, 'Matteo')");
db.ExecuteNonQuery("INSERT INTO tb1 (a, b) VALUES (20, 'Mauro')");

db.ExecuteNonQuery("CREATE TABLE tb2 (a NUMBER NOT NULL, b CHAR(20))");
db.ExecuteNonQuery("INSERT INTO tb2 (a, b) VALUES (10, 'San Francisco')");
db.ExecuteNonQuery("INSERT INTO tb2 (a, b) VALUES (20, 'Cuppertino')");

// A Store Procedure cannot Return Value
StringBuilder sp1 = new StringBuilder();
sp1.Append("CREATE OR REPLACE PROCEDURE tb2sp1 ");
sp1.Append("IS ");
sp1.Append("BEGIN ");
sp1.Append("INSERT INTO tb1 (a, b) VALUES (30, 'SP1 TEST'); ");
sp1.Append("END; ");
db.ExecuteNonQuery(sp1.ToString());

// A Function can Return a Value
StringBuilder sp2 = new StringBuilder();
sp2.Append("CREATE OR REPLACE function tb2sp2 (idx NUMBER) ");
sp2.Append(" RETURN NUMBER ");
sp2.Append("IS ");
sp2.Append(" var_count NUMBER; ");
sp2.Append("BEGIN ");
sp2.Append(" SELECT COUNT(*) INTO var_count FROM tb1; ");
sp2.Append(" return (var_count + idx); ");
sp2.Append("END; ");
db.ExecuteNonQuery(sp2.ToString());

List r1 = db.Execute("select * from tb1");
List r2 = db.Execute("select a, b, (a * 2 + 1) from tb1");
List r3 = db.Execute("select tb1.a as ID, tb1.b as NAME,
                              tb2.b as PLACE from tb1 INNER JOIN tb2 ON tb1.a = tb2.a");
db.ExecuteStoredProcedure("tb2sp1");
List r4 = db.Execute("select * from tb1");
object sp2RetVal = db.ExecuteFunction("tb2sp2(10)");

db.ExecuteNonQuery("DROP PROCEDURE tb2sp1");
db.ExecuteNonQuery("DROP FUNCTION tb2sp2");
db.ExecuteNonQuery("DROP TABLE tb2");
db.ExecuteNonQuery("DROP TABLE tb1");

db.Disconnect();

Here you can find the Source Code: Oracle for Beginners Source Code.

The OracleDatabase class that you’ve seen in the example above, is a simple wrapper class, that you can see below.
As always, we’ve two methods for Connect and Disconnect from Database Server.


public bool Connect(string sid, string userId, string password) {
    string cs = String.Format("Data Source={0}; User Id={1};
	                           Password={2};", sid, userId, password);
    _oracle = new OracleConnection(cs);
    _oracle.Open();
    return (_oracle.State == ConnectionState.Open);
}

public void Disconnect() {
    if (_oracle != null && _oracle.State != ConnectionState.Closed)
        _oracle.Close();
}

Below there’re the methods that helps you to retrieve SELECT data, and to run non query like INSERT, UPDATE, DELETE, DROP…


public List Execute(string query, params object[] args) {
    using (OracleCommand cmd = new OracleCommand(String.Format(query, args), _oracle)) {
        cmd.CommandType = CommandType.Text;
        return (Execute(cmd));
    }
}

private List Execute(OracleCommand cmd) {
    List dataRecordList = new List();
    using (OracleDataReader reader = cmd.ExecuteReader()) {
        while (reader.Read()) {
            DataRecord record = new DataRecord();
            for (int i = 0; i < reader.FieldCount; ++i)
                record.Add(reader.GetName(i), reader[i]);
            dataRecordList.Add(record);
        }
        reader.Close();
    }
    return (dataRecordList);
}

public int ExecuteNonQuery(string query, params object[] args) {
    using (OracleCommand cmd = new OracleCommand(String.Format(query, args), _oracle)) {
        cmd.CommandType = CommandType.Text;
        return(cmd.ExecuteNonQuery());
    }
}

Below two methods to Execute a Function and a Stored Procedure, functions can have a return value.


public object ExecuteFunction(string query, params object[] args) {
    using (OracleCommand cmd = new OracleCommand(String.Format(query, args), _oracle)) {
        cmd.CommandType = CommandType.StoredProcedure;
        OracleParameter retParameter = new OracleParameter();
        retParameter.Direction = ParameterDirection.ReturnValue;
        retParameter.OracleType = OracleType.Number;
        cmd.Parameters.Add(retParameter);
        cmd.ExecuteNonQuery();
        return (retParameter.Value);
    }
}

public int ExecuteStoredProcedure(string query, params object[] args) {
    using (OracleCommand cmd = new OracleCommand(String.Format(query, args), _oracle)) {
        cmd.CommandType = CommandType.StoredProcedure;
        return (cmd.ExecuteNonQuery());
    }
}

C# Parallel Foreach using Thread Pool

Matteo Bertozzi — Fri, 26 Dec 2008 12:56:56 +0000


public void Foreach(T[] array, Action action)
{
   int cpus = 2 * Environment.ProcessorCount;
   int nitems = array.Length;
   int chunk = nitems / cpus;
   int counter = cpus;

   using (AutoResetEvent signal = new AutoResetEvent(false))
   {
      for (int i = 1; i <= cpus; i++)
      {
         ThreadPool.QueueUserWorkItem(delegate(object o)
         {
            int unit = (int)o;

            for (int j = (unit - 1) * chunk;
                  j < (unit == cpus ? nitems : unit * chunk);
                  j++)
            {
               action(array[j]);
            }

            if (Interlocked.Decrement(ref counter) == 0)
            signal.Set();
         }, i);
      }

      signal.WaitOne();
   }
}


public void ForeachWithResults(T[] array, T1[] results, Action action)
{
   int cpus = 2 * Environment.ProcessorCount;
   int nitems = array.Length;
   int chunk = nitems / cpus;
   int counter = cpus;

   using (AutoResetEvent signal = new AutoResetEvent(false))
   {
      for (int i = 1; i <= cpus; i++)
      {
         ThreadPool.QueueUserWorkItem(delegate(object o)
         {
            int unit = (int)o;

            for (int j = (unit - 1) * chunk;
                  j < (unit == cpus ? nitems : unit * chunk);
                  j++)
            {
               action(j, array[j], results);
            }

            if (Interlocked.Decrement(ref counter) == 0)
               signal.Set();
         }, i);
      }

      signal.WaitOne();
   }
}

C#: Evaluating Infix Expression

Matteo Bertozzi — Sat, 20 Dec 2008 18:26:04 +0000

This morning I’ve written a simple Infix Notation Evaluator in C, and this afternoon I’ve rewritten it in C#. I Think that C# is more easy to understand than C, so I’ve posted the C# Example. (If you want the C example, ask me).
In few words, I take the Input in “Infix Notation” and I convert it in Reverse Polish Notation (RPN), and then the RPN string is evaluated.

First Example: Evaluating a simple Math Expression.

string expr = "10 + 5 - (2 + (3 * 4) + (5 * 3)) - 4 ^ 2 << 8";
Operation operation = new MyTokener().Parser(expr);
Console.WriteLine("{0} = {1}", expr, operation.Evaluate());

Second Example: Evaluating a simple Math Expression with variables.

Dictionary vars = new Dictionary();
vars.Add("A", "1"); vars.Add("B", "2");
vars.Add("C", "3"); vars.Add("D", "4");
vars.Add("K", "5"); vars.Add("L", "6");

string expr = "(A + B) + C + (D * (K + (L - 1)))";
Operation operation = new MyTokener().Parser(expr);
Console.WriteLine("{0} = {1}", expr, operation.Evaluate());

Third example: Evaluating simple String expression.

string expr = "'Hello' + ' ' * 3 + \"World\"";
Operation operation = new MyTokener().Parser(expr);
Console.WriteLine("{0} = {1}", expr, operation.Evaluate());

After the Example you can find the Source Code Here (You can compile it under Linux with gmcs).

That's all folks! I'm really busy with the Real Work, I'm waiting the 25th for taking a break.

Qyoto – First Experiment

Matteo Bertozzi — Fri, 18 Jul 2008 13:02:12 +0000

A little example of Mono, C# and Qt4 (Qyoto).
This examples contains all what you need to starting a little application. QtDesigner, Resources, and Slot handling.

If you’re using Ubuntu, you must install libqyoto4.3-cli and qyoto-dev-tools.

Qt User Interface Compiler (uic) for C# is called uics and (in ubuntu) you can find it here: /usr/lib/kde4/bin/

Qt Resource Compiler (rcc) for C# is called csrcc and is in the same path of uics.

To define Slots you should add attribute [Q_SLOT("slotName()")] on slot Method.

Another thing to remember is that all methods start with Upper case, so you’ve to call textEdit.SetText(”myText”) and not textEdit.setText(”myText”) like in C++.

Source Code of the example could be downloaded from here: QyotoTest