Andrew Seaford

Test if two values are almost equal.

/// 

/// Test if two doubles are approximately equal
/// 
/// Test variable one
/// Test variable two
/// epsilon a measure of equality
/// boolean true = values are approximately equal, false = values are not equal
public static Boolean almostEqual(double a, double b, double eps)
{
    return Math.Abs(a - b) < eps;
}

Example using the function.

double a = 1.234;
double b = 1.235;
double eps = 0.01;
Console.WriteLine("equal = " + almostEqual(a, b, eps).ToString());

A simple SQL example of using the To_Date function to format a date.

INSERT INTO EXAMPLETBL (EXAMPLEID, EXAMPLEDATE) VALUES ('5', TO_DATE('2014-05-08 08:06:24', 'YYYY-MM-DD HH24:MI:SS'))

This simple batch script creates a new folder based on the date and time and then executes a oracle database dump.

REM Backup oracle database

@echo Starting database backup

REM get the current datestamp in the format year-month-day-hour-minute
SET DATESTAMP=%date:~6,4%-%date:~3,2%-%date:~0,2%-%time:~0,2%-%time:~3,2%

REM Create a new directory
md "c:\backup\%DATESTAMP%"

REM backup database
REM Dont forget to change username and password
exp username/password@xe FILE="c:\backup\%DATESTAMP%\databasename.dmp"

@echo Finished backing up database to c:\backup\%DATESTAMP%

/** split a name into the first name and last name
 * @param input The name eg 'John Doe'
 * @return Array containing firstname and lastname eg array('firstname'=>'John', 'lastname'=>'Doe');
 */
function splitname($input)
{
   $output = array("firstname"=>"", "lastname"=>"");
   $space = strpos($input, " ");
   if ($space !== false)
   {
      $output['firstname'] = substr($input, 0, $space);
      $output['lastname'] = substr($input, $space, strlen($input));     
   }
   else
   {
      $output['lastname'] = $input;
   } 
   return $output;
}

Convert a url data in to Name Value Pairs array.

/** Convert a url data in to Name Value Pairs array
 * @param url The url and the data string
 * @return array of named value pairs
 */
function urlToNvp($url)
{
   $output = array();
   
   $questionmark = strpos($url, '?');
   if ($questionmark !== false)
   {
      $url = substr($url, $questionmark+1, strlen($url));
   }   
   
   foreach(explode('&', $url) as $data)
   {
      $value = explode('=', $data);
      $output[$value[0]] = $value[1];
   }
      
   return $output;
}

Here are three examples of using this function

print_r(urlToNvp("www.example.co.uk?p1=one&p2=two"));
print_r(urlToNvp("p1=one&p2=two"));
print_r(urlToNvp("www.example.co.uk?p1=one"));

The result

Array ( [p1] => one [p2] => two )
Array ( [p1] => one [p2] => two )
Array ( [p1] => one )

In this example I will create a C++ dll that with contain the OpenCV image processing code. I then will create a C# WPF application, within this application i will then include the dll and using the image processing function.

1. Install OpenCV http://docs.opencv.org/doc/tutorials/introduction/windows_install/windows_install.html#windows-installation
2. Create a C++ Win32 console Application, in this example it will be called ImageProcessingAgain
3. Click Next. Select Application type dll. Then click finish.
4. Click Property Manager, right click on debug, then select ‘Add Existing Property Sheet’. If you dont have a property sheet follow the following tutorial for creating The Local Method http://docs.opencv.org/doc/tutorials/introduction/windows_visual_studio_Opencv/windows_visual_studio_Opencv.html
5. Add the following code to the cpp

   // ImageProcessAgain.cpp : Defines the exported functions for the DLL application.
   //
   
   #include "stdafx.h"
   
   #include "opencv\cv.h"
   #include "opencv\highgui.h"
   
   extern "C"
   {   
   	__declspec(dllexport) int exampleImageProcessing(LPCWSTR);
   }
   
   extern int __cdecl exampleImageProcessing(LPCWSTR filename)
   {
   	IplImage* img = cvLoadImage((char*)filename);
   	return img->width;
   }
   

6. build the dll project
7. Create a C# WPF project called UsingOpencvAgain
8. copy the dll and then include the dll within the C# project
9. Select the dll in the solution explorer, set the ‘copy to output directory’ property to ‘copy if newer’
10. Create two textboxes and a button
11. Add the following C# code to the application

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Windows;
    using System.Windows.Controls;
    using System.Windows.Data;
    using System.Windows.Documents;
    using System.Windows.Input;
    using System.Windows.Media;
    using System.Windows.Media.Imaging;
    using System.Windows.Navigation;
    using System.Windows.Shapes;
    using System.Runtime.InteropServices;
    
    namespace UsingOpencvAgain
    {
        /// 
    
        /// Interaction logic for MainWindow.xaml
        /// 
        public partial class MainWindow : Window
        {
            public MainWindow()
            {
                InitializeComponent();
            }
    
            [DllImport("ImageProcessAgain.dll", CallingConvention = CallingConvention.Cdecl)]
            public static extern int exampleImageProcessing(string filename);
    
            private void button1_Click(object sender, RoutedEventArgs e)
            {
                textBox2.Text = exampleImageProcessing(textBox1.Text).ToString();
            }
        }
    }
    
    

A very simple method for writing to a file, not forget to include using System.IO;.

string filename = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments) + @"\test.txt";
string content = "This is the new file content";
File.WriteAllText(filename, content);

The setName funcion demostrates simple data validation on the argument value.

void setName(string value)
{
    // validate empty
    if (string.IsNullOrWhiteSpace(value))
    {
        throw new ArgumentNullException("Please enter a value");
    }

    // validate length
    if (value.Length > 10)
    {
        throw new ArgumentException("The value is too long");
    }

    // value is valid
    MessageBox.Show("The value is valid");
}

When calling the setName function it is important that we implement code to catch any exceptions

try
{
    setName(textBox1.Text);
}
catch (Exception ex)
{
    MessageBox.Show("Error " + ex.Message);
}

A var type can be checked using the ‘is’ statement

var a = 1.0;

if (a is int)
{
    MessageBox.Show("int");
}
else
{
    MessageBox.Show("is NOT int");
}

The code below shows the short hand and long hand syntax for defining class properties.

public class Example
{
  // class property short hand
  public string Firstname {get; set;}


  // class property long hand
  private string _Lastname;
  public string Lastame
  {
     get {return _Lastname}
     set {_Lastname = value}
  }
}