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CSharp - Rijndael/AES symetric Encryption and Decryption

Posted on February 2nd, 2006 by gernot.
Categories: CSharp.

A short tutorial how to encrypt, respectivelly decrypt a string in C# with Rijndael/AES.

NOTE: The Keygeneration is done in the encryption and decryption methods. For usage in a ‘real’ application this should be outsourced.

Encryption

using System.Security.Cryptography;

// Input Values:
// pwdHash = “MD5″ / “SHA1″
// iv = “16 ASCII Characters”
// keySize = 128 / 192 / 256
public string Encrypt(string text, string pwdPhrase, string pwdSalt, string pwdHash,
  int pwdIterations, string iv, int keySize)
{
  byte[] ivBytes = Encoding.ASCII.GetBytes(iv);
  byte[] pwdSaltBytes = Encoding.ASCII.GetBytes(pwdSalt);
  byte[] textBytes = Encoding.UTF8.GetBytes(text);
  PasswordDeriveBytes pwd
     = new PasswordDeriveBytes (pwdPhrase, pwdSaltBytes, pwdHash, pwdIterations);
  byte[] keyBytes = pwd.GetBytes( keySize / 8 );
  RijndaelManaged symmKey = new RijndaelManaged ();
  symmKey.Mode = CipherMode.CBC;
  ICryptoTransform enc
     = symmKey.CreateEncryptor(keyBytes, ivBytes);
  MemoryStream mem = new MemoryStream ();
  CryptoStream cry
     = new CryptoStream (mem, enc, CryptoStreamMode.Write);
  cry.Write(textBytes, 0, textBytes.Length);
  cry.FlushFinalBlock();
  byte[] cipBytes = mem.ToArray();
  mem.Close();
  cry.Close();
  return Convert.ToBase64String(cipBytes);
}

Decryption

using System.Security.Cryptography;

// Input Values:
// pwdHash = “MD5″ / “SHA1″
// iv = “16 ASCII Characters”
// keySize = 128 / 192 / 256
public string Decrypt(string cip, string pwdPhrase, string pwdSalt, string pwdHash,
  int pwdIterations, string iv, int keySize)
{
  byte[] ivBytes = Encoding.ASCII.GetBytes(iv);
  byte[] pwdSaltBytes = Encoding.ASCII.GetBytes(pwdSalt);
  byte[]cipTextBytes = Convert.FromBase64String(cip);
  PasswordDeriveBytes pwd
     = new PasswordDeriveBytes (pwdPhrase, pwdSaltBytes, pwdHash, pwdIterations);
  byte[] keyBytes = pwd.GetBytes( keySize / 8 );
  RijndaelManaged symmKey = new RijndaelManaged ();
  symmKey.Mode = CipherMode.CBC;
  ICryptoTransform dec
     = symmKey.CreateDecryptor(keyBytes, ivBytes);
  MemoryStream mem = new MemoryStream (cipTextBytes);
  CryptoStream cry
     = new CryptoStream (mem, dec, CryptoStreamMode.Read);
  byte[] textBytes = new byte[cipTextBytes.Length];
  int decByteCount
     = cry.Read(textBytes, 0, textBytes.Length);
  mem.Close();
  cry.Close();
  return Encoding.UTF8.GetString(textBytes, 0, decByteCount);
}

2 comments.

CSharp - Replace embedded Wildcard in String

Posted on February 2nd, 2006 by gernot.
Categories: CSharp.

A small method for replacing an embedded wildcard in a string.

simple example

String: [GG] is 24 [Y] old
[GG] should be replaced with Gernot Goluch and [Y] with year

usefull example

One possible usage would be including different IDs of xml elements or db entries in other entries by using wildcard delimiters in some content of the entry.

E.g. xml processing

‹testNode id=“123″›BlaBla‹/testNode›
‹testNode id=”456″›BlaBla and [123] is really dumb content‹/testNode›

After processing the content of testNode with id “456″ the content would be:
“BlaBla and Blabla is really dumb content”

Method Call

The method call for the simple example above.

replaceWildCardInString(“[GG] is 24 [Y] old”,new char[] {‘[', ']‘});

The Method

The method for the simple example above.

public string replaceWildCardInString(string _string, char[] _wildCard) {
  if (_string.IndexOf(_wildCard[0]) == -1) return _string;
  else {
    //split string and get content to replace
    string[] contentSplit = _string.Split(_wildCard);
    //What is inbetween the wildcards
    string contentToReplace = contentSplit[1];
    //The ‘real’ content
    //***Add Code here how to get the real content***
    //E.g.: very simple. Possible inclusion of db or xml query/method call
    string contentReplace = “”;
    if (contentToReplace.Equals(“GG”)) contentReplace = “Gernot Goluch”;
    else if (contentToReplace.Equals(“Y”)) contentReplace = “year”;
    //replace the wildcard with the ‘real’ content
    //and check if other wildcards are in the content
    WildCardClass wcc = new WildCardClass();
     return wcc.replaceWildCardInString(
        _string.Replace(
        _wildCard[0] + contentToReplace + _wildCard[1]
        , contentReplace)
        , _wildCard);
  }
}

0 comments.

CSharp - XML Validation with XML Schema

Posted on January 30th, 2006 by gernot.
Categories: CSharp.
Tags: .NET, C#, code, schema, validation, xml

This is a short tutorial how one can validate a XML Document against a XML schema by using C# and the .NET framework.

C# Class

using System.Xml;
using System.Xml.Schema;

namespace XMLValidation
{
class XMLValidatorTest
{

private bool XMLisValid = true;

public void ReadValidateXMLFile()
{
   XmlTextReader reader = new XmlTextReader(“C:\\test.xml”);
   XmlValidatingReader validator = new XmlValidatingReader(reader);
   validator.ValidationType = ValidationType.Schema;
   validator.ValidationEventHandler +=
      new ValidationEventHandler(this.XMLValidationEventHandler);

   while (validator.Read())
   {
      //Add code here to process XML content
   }
   validator.Close();

   //Check if XML document is valid or not
   if (this.XMLisValid)
      Console.WriteLine(“XML Document is valid”);
   else
      Console.WriteLine(“XML Document is invalid”);
   }
}

public static void XMLValidationEventHandler(
  object sender,ValidationEventArgs args)
{
   this.XMLisValid = false;
   Console.WriteLine(“XML Validation event” + args.Message);
}

}
}

XML Root Node - XSD Reference

In the XML File:

‹?xml version=”1.0″ encoding=”utf-8″ ?›
‹testNS:testRoot
  xmlns:testNS=”http://www.gego.info/testxmlns”
  xmlns:xsi=”http://www.w3.org/2001/XMLSchema-instance”
  xsi:schemaLocation=”http://www.gego.info/testxmlns test.xsd”›

In the XSD File:

‹?xml version=”1.0″ encoding=”utf-8″ ?›
‹xs:schema
  id=”test”
  targetNamespace=”http://www.gego.info/testxmlns”
  elementFormDefault=”qualified”
  attributeFormDefault=”unqualified”
  xmlns=”http://www.gego.info/testxmlns”
  xmlns:xs=”http://www.w3.org/2001/XMLSchema”›

0 comments.

CSharp - Create and Use User Controls

Posted on January 25th, 2006 by gernot.
Categories: CSharp.
Tags: .NET, C#, code, gui

This is a short Tutorial how to create and use User Controls in the .NET Framework (C#):

Create and Use User Control in Visual Studio

1. Create a new Solution: MyMainApplication.sln & MyMainApplication.csproj
   1. Create a new Windows Form: Form1.cs
2. In Solution:
   1. Add >>
   2. New Project >>
   3. Windows Control Library: MyUserControlLibrary.csproj
3. In MyMainApplication.csproj:
   1. Right Click References >>
   2. Add Reference >>
   3. Tab: Projects >>
   4. Mark MyUserControlLibrary.csproj >>
   5. OK
4. In MyUserControlLibrary.csproj:
   1. Right Click on Project >>
   2. Add >>
   3. User Control >>
   4. MyUserControl1.cs
5. Drag&Drop Controls to MyUserControl1 in Visual Studio Designer (or add manually if you like)
6. In Visual Studio Menu:
   1. Build >>
   2. Build Solution
7. In Visual Studio Designer for Form1.cs you can find the MyUserControl1 Control in the toolbox and drag&drop them to your Form
8. Note: If you make changes to the UserControl (MyUserControl1) you have to rebuild the solution everytime to see the changes in your Main Form (Form1)

Event Firing from User Control to Application

Here I want to describe how one can fire an event (e.g.: from a button) in the UserControl and notify the Main Application, which uses the User Control:

In MyUserControl1.cs:

//Just a TestString
public string TestString = “Test123″;
// Declare delegate Button1 clicked.
public delegate void Button1_ClickHandler();
// Declare the event, which is associated with our delegate
[Category("Action")] [Description("Fires when the Button1 is clicked.")]
public event Button1_ClickHandler Button1_Clicked;
// Handler for Button1
// NOTE: Don’t forget to add this Handler to the Button itself
private void Button1_Click(object sender, System.EventArgs e)
{
    if (Button1_Clicked != null)
      // Notify Subscribers
      Button1_Clicked();
    else
      Console.WriteLine(“No Subscribers for Button1″);
}

In Form1.cs:

// NOTE: Don’t forget to add this Handler to the UserControl itself
private void MyUserControl11_Button1_Clicked()
{
    Console.WriteLine(“Button1 was clicked in MyUserControl11, TestString:”
    + MyUserControl11.TestString);
}

0 comments.

CSharp - Kategorie, was soll das?

Posted on January 25th, 2006 by gernot.
Categories: CSharp.

Nachdem ich mich seit längerer Zeit ein mit C# und dem .NET Framework programmiere und selbst immer alle möglichen Dinge, die ich schon einmal gemacht habe vergesse, möchte ich in dieser Rubrik eine kleine Sammlung an nützlichen Code Snippets präsentieren bzw. Links zu guten Tutorials anbieten.

1 comment.