using System;
using System.Data.SqlClient;

namespace ConsoleCSharp
{
	/// <summary>
	/// Summary description for Class1.
	/// </summary>
	class DataReader_SQL
	{
		/// <summary>
		/// The main entry point for the application.
		/// </summary>
		[STAThread]
		static void Main(string[] args)
		{
			//
			// TODO: Add code to start application here
			//
			try
			{
		    	SqlConnection thisConnection = new SqlConnection(@"Network Library=DBMSSOCN;Data Source=192.168.0.100,1433;database=Northwind;User id=Paladine;Password=;");
				thisConnection.Open();
		 	SqlCommand thisCommand = thisConnection.CreateCommand();
		 	thisCommand.CommandText = "SELECT CustomerID, CompanyName FROM Customers";
			 SqlDataReader thisReader = thisCommand.ExecuteReader();
				while (thisReader.Read())
				{
		 		Console.WriteLine("\t{0}\t{1}", thisReader["CustomerID"], thisReader["CompanyName"]);
					}
				thisReader.Close();
				thisConnection.Close();

			}
			catch (SqlException e)
			{
				Console.WriteLine(e.Message);
			}
			
		}
	}
}

...
Sqldataadapter custAdapter = new SqlDataAdapter("SELECT * FROM Customers", thisConnection);
custAdapter.Fill(thisDataSet, "Customers");
foreach (DataRow custRow in thisDataSet.Tables["CustomerID"].Rows)
{ 
		if (custRow["City"].ToString() == "Madrid")
			   {
				 Console.WriteLine("Customer ID: " + custRow["CustomerID"]);
				}
}