Practical C# Codes

Converting XML to String

2010-07-24T14:55:00.000-07:00

In this short post I will show you how to convert XML to String, o viceversa, in order for example, to send it via Tcp/Ip.

In this example, a Client is going to genereta a XML Document and convert it to string.

The Server side must recive the string and generate the XML.

(Here you will not see how the communication is done, for example the convertion between string and stream)

Client Code:

XmlDocument xmlDoc = new XmlDocument();

xmlDoc.Load(@"C:\XML\" + test + ".xml");

//Getting the Xml as String

String message = xmlDoc.InnerXml;

client.Send(message);

Server Code:

String innerXml = response;

XmlDocument xmlServer = new XmlDocument();

//Set the string to the Xml created above

xmlServer.InnerXml = innerXml;

More XML options in C#

2010-07-20T16:16:00.000-07:00

Continuing the xml posts, in this oportunity I will show you more options to create your XmlDocument.

Here we will see:

- Adding comment to the xml document (XmlComment)

- Adding fragment (XmlDocumentFragment)

- Creation of attributes (XmlAttribute)

- Adding information about the document Type (XmlDocumentType)

- And also, declarations and elements

Code:

XmlDocument xmlDoc = new XmlDocument();

XmlDeclaration xmlDec = xmlDoc.CreateXmlDeclaration("1.0", "UTF-8", null);

xmlDoc.AppendChild(xmlDec);

XmlElement root = xmlDoc.CreateElement("root-element");

//Adding info about the document type

XmlDocumentType docType = xmlDoc.CreateDocumentType("BOOKS", null, null, null);

xmlDoc.AppendChild(docType);

XmlAttribute xmlAtt = xmlDoc.CreateAttribute("attribute");

xmlAtt.Value = "value_for_xmlAtt";

root.SetAttributeNode(xmlAtt);

xmlDoc.AppendChild(root);

//Placing a comment in the Xml

XmlComment xmlComment = xmlDoc.CreateComment("First Book information");

root.AppendChild(xmlComment);

XmlElement book1 = xmlDoc.CreateElement("book-1");

book1.SetAttribute("name", "Harry Potter");

root.AppendChild(book1);

//Creating a Fragment

XmlDocumentFragment xmlDocFragment = xmlDoc.CreateDocumentFragment();

xmlDocFragment.InnerText = "---------Inner text-------";

xmlDoc.DocumentElement.AppendChild(xmlDocFragment);

XmlElement book2 = xmlDoc.CreateElement("book-2");

book2.SetAttribute("name", "Robles");

root.AppendChild(book2);

xmlDoc.Save(@"C:\XML\" + "xmlTest.xml");

Output:

Xml document edition

2010-07-17T11:41:00.000-07:00

In the previous post I showed you how to create a XmlDocument following some easy steps. The idea now is to read the created xml and find elements by a specific tag. Then we are going to change that value and save the edited xml.

Code:

For the first book element, we are going to add inner text:

XmlDocument xmlDoc = new XmlDocument();

//Load the Xml created previously

xmlDoc.Load(@"C:\XML\" + "xmlTest.xml");

XmlNodeList books;

books = xmlDoc.GetElementsByTagName("book-1");

//Since there is only one element with this tag, the loop is not necessary.

foreach (XmlNode node in books)

{

node.InnerText = "Great Book";

}

For the second element, we are changing the attributes values:

books = xmlDoc.GetElementsByTagName("book-2");

foreach (XmlNode node in books)

{

node.Attributes[0].Value = "Time";

}

xmlDoc.Save(@"C:\XML\" + "xmlTest.xml");

Output:

Xml Document creation using DOM

2010-07-16T08:54:00.000-07:00

In this article I´ll show you how to create a .xml document using proper tags and definitions. To do this you need to import the System.Xml library.

The idea is simple and the best way to learn this is by a small example.

Here I´ll create a XmlDocument with a couple of child elements.

Code:

XmlDocument xmlDoc = new XmlDocument();

//First, create the declaration

XmlDeclaration declaration = xmlDoc.CreateXmlDeclaration("1.0", "UTF-8", null);

xmlDoc.AppendChild(declaration);

XmlElement books = xmlDoc.CreateElement("BOOK");

xmlDoc.AppendChild(books);

//Child 1 for BOOK

XmlElement book1 = xmlDoc.CreateElement("book-1");

book1.SetAttribute("name", "Harry Potter");

books.AppendChild(book1);

//Child 2 for BOOK

XmlElement book2 = xmlDoc.CreateElement("book-2");

book2.SetAttribute("name", "People");

book2.SetAttribute("type", "magazine");

books.AppendChild(book2);

//Save the Xml

xmlDoc.Save(@"C:\XML\" + "xmlTest.xml");

Output:

Split function in C#

2010-05-08T17:06:00.000-07:00

Here is a small post about using split function in c#. We are going to split a String by using delimiters. A delimiter will tell when to split the string. So here is a fragment of code to perform splitting.

String answer = "This$is|a|string";

char[] delimitator1 = new char[] { '$' };

char[] delimitator2 = new char[] { '|' };

string[] words = answer.Split(delimitator1);

Console.WriteLine("First word : " + words[0]);

//Note that now we split the second part of the string

String allRest = words[1];

string[] rest1 = allRest.Split(delimitator2);

Console.WriteLine("Second word : " + rest1[0]);

Console.WriteLine("Third word : " + rest1[1]);

Console.WriteLine("Fourth word : " + rest1[2]);

Output:

Get integer sequence primary key in C#

2009-04-18T12:25:00.000-07:00

Here is a nice method of getting the primary key from a table. Basicly what I do here is obtanning the first available key to insert new rows with this obtained key.

First we set the instance of the connection with the database and then we create a sql command. After this, we open the connection and execute the command directly to the database.
If everything executes correctly, we will obtain the first available key. If not, an exception is going to be raised.

public int GetOid()

{

OleDbConnection conn = ConnectionMgr.GetInstance().GetConnection();

OleDbCommand cmd = new OleDbCommand("Select * From Oid", conn);

int oidNum = 0;

try

{

conn.Open();

oidNum = (int)cmd.ExecuteScalar();

oidNum++;

cmd = new OleDbCommand("UPDATE Oid SET lastOid=" + oidNum, conn);

cmd.ExecuteNonQuery();

}

catch (OleDbException ex)

{

throw new DatabaseException("Error updating oid", ex);

}

finally

{

conn.Close();

}

return oidNum;

}

Adding new line to a txt file in C# .Net

2008-11-28T15:10:00.000-08:00

In this very short article I will show you the easiest way to add a new text line on a txt file using C# .NET.

I was researching on this matter very hard. First I started to read the entire file to the end and then add the new line. There is a small problem on doing this: it might work at compilation time but when you execute the application, you will see an error that says that two processes cannot run at the same time. Sound fair.
Then I started working with locks. There are a couple of locks, the lock when you read and the lock when you write. This is good stuff to talk later but not right now.

So what is the easiest solution to this matter, here it is:

public void AddNewLine(String text)
{
File.AppendAllText("C:\\Logs.txt", text + Environment.NewLine);
}

Yes, just like that.
And if you want to read the txt file, you could do something like this:

public String ReadAll() {

StreamReader sr = new StreamReader("C:\\Logs.txt");
String allText = sr.ReadToEnd();
return allText;

}

Understanding Exceptions provided by the .NET Framework - Part 2.

2008-08-30T08:32:00.000-07:00

You may saw in the previous post, a couple of exceptions we can use that are provided by the .Net Framework derived from the System.Exception class. Those two exceptions were: The StackOverflowException and the NullReferenceException.
Now I will describe to you the OutOfMemoryException and the DivideByZeroException.

The OutOfMemoryException

This exception is thrown by the CLR when your machine runs out of memory. Every time you create an object using new, some memory will be reserved for it. In case there is now enough memory, the exception will be triggered.
Let´s write an example now. Supose you want to create a Hashtable that allocated a large capacity. If there is no memory to do this, the CLR throws the exception.
Take a look at this C# example:

using System;

using System.Collections.Generic;

using System.Collections;

using System.Linq;

using System.Text;

namespace ConsoleApplication5

{

class Program

{

static void Main(string[] args)

{

try

{

Hashtable hatb = new Hashtable(91230000);

}

catch (OutOfMemoryException)

{

Console.WriteLine("CLR out of memory");

}

Console:

The DivideByZeroException

This exception is quite simple: when you are dividing by 0, the CLR throws this exception.
Take a look at this example:

class Program

{

static void Main(string[] args)

{

int a = 5;

int b = 0;

try {

int res = a / b;

}

catch(DivideByZeroException){

Console.WriteLine("You are dividing by 0");

}

Console:

Understanding Exceptions provided by the .NET Framework - Part 1.

2008-08-22T13:48:00.000-07:00

The NullReferenceException:

The easiest way to explain how this works is by writing an example. What we are going to do in the following example is quite simple: we are going to create an Object and initialize it with null value. This object contains string public value type that we can malipulate. But in this particulare case, our Object was set to null, so the CLR will catch this particular exception:

Class Person

public class Person

{

public String name;

}

Main:

static void Main(string[] args)

{

try

{

Person p = new Person();

p = null;

p.name = "CoderG";

}

catch (NullReferenceException) {

Console.WriteLine("p set tu null, cannot be referenced");

}

Console:

The StackOverflowException:

This exception is catch by the CLR when it runs out of stack memory. Be aware that the CLR has a finite amount of stack space, so if it gets full, the StackOverflowException will catch the exception. An easy way to trigger this is by defining a recursive function that does nothing, just call itself. Eventually, if the stack was infinite, this method will never stop, but because it is finite, the exception catches this:

Main:

static void Main(string[] args)

{

try

{

callMe();

}

catch (StackOverflowException) {

Console.WriteLine("Stack run out of memory!!!!");

}

public static void callMe(){

callMe();

}

Console:

Using destructors in C#

2008-08-06T12:28:00.000-07:00

Destructors are similar to de Constructors, almost the oposite.
The destructor is used by the CLR when objects are destroyed.
All this process happens in the background so the developer does not have to preocupate about deleting
created objects. Writing a destructor is not necessary but if you are going to create one in your class,
you can only add one.

The Destructors sintaxis are very similar to the constructors.
They start with the simbole ~ and the name must be the same to the class.
Also, there are a few particulares things about destructors you should know:
-No parameters are allowed here.
-As said before, you can only write one.
-You can not call a constructor like you will normally do with a method. They are automatically used by the CLR (by the garbage collection).
-No overload or inheritances are allowed.

So let’s write a small C# class.

-Class Plane

using System;
using System.Text;

class Plane
{
public String type;
public String company;

public Plane(String t, String c){
type = t;
company = c;
Console.WriteLine("Constructor in action\n");

}

~Plane() {
type = "N/A";
company = "N/A";
Console.WriteLine("Destructor in action");
}

}

- Main

static void Main(string[] args)
{

Plane p = new Plane("AirBus", "Tam");

}

- Console

Defining methods in Structures (C#)

2008-08-04T09:19:00.000-07:00

Normally you will see structures with only variables on it, but methods can also be included. This is usefull when you need to write a method that works directly with the content of the stuct.

- The first method that I will create inside the structure is a constructor. Remember that there can be many constructores as long as the parameter list is different of each other.
- The second method you will see next is a simple bool method that return true if both values of the structure varaibles (integers) are 50.

Ok, lets now proceed to write this example.

using System;

class Program
{

struct Point {

public int x;
public int y;

public Point(int x1, int y1) {

x = x1;
y = y1;
}

public bool check50() {

if ((x == 50) && (y == 50))
return true;

return false;

}
}

Main:

static void Main(string[] args)
{
Point p = new Point(50 , 50);
Point p2 = new Point(10, 20);

if (p.check50())
Console.WriteLine("Point p is at 50s");

else
Console.WriteLine("Point p not at 50s");

if(p2.check50())
Console.WriteLine("Point p2 is at 50s");

else
Console.WriteLine("Point p2 not at 50s");
}
}

Console:

Implementing Interfaces in C#

2008-07-31T09:23:00.001-07:00

Interfaces are a set of methods, properties and event that provides functionalities. This interces can be implemented by C# classes or structures.

Interfaces do not provide methods of their own. They only contain methods identifiers, return values and parameters.
This is very useful when you have certain behaviour that need to follow a set of operations, such as manipulating a Data Base.
C# classes are allowed to implement many interfaces.

Implementing an Interfaz in a class says that the class must provide implementation to all of the methods signatures from the interface.

Let’s write a small C# example. In this example you will see of to implement interfaces that contain methods signatures and how a class implements this interface.

Code:

interface Interface1
{

void Method1();
void Method2();

}

public class Class1 : Interface1
{

public void Method1()
{
//Implementation of the method
}

public void Method2() { }

}

Now, you can also use interfaces that the .NET Frameworks has. In this example you will see how to implement the Idisposable interface. The Idisposable interface supports a method called Dispose(). It also supports a constructor and a destructor.

Also you will see in the Main class, the keyword using. It is used to create a new object and can be manipulated only within the braces ({}). After the close brace is reached, the object will be automatically destroyed.

Code:

class Class2 : IDisposable
{

public Class2()
{
Console.WriteLine("Constructor");
}

~Class2()
{
Console.WriteLine("Destuctor");
}

public void Dispose()
{
Console.WriteLine("Dispose from IDisposable.Dispose");
}

}

Main:

class Program
{

static void Main(string[] args)
{

using (Class2 myC = new Class2()) { }
}
}

Console:

MessageBox using AbortRetryIgnore Button in C#

2008-07-17T14:07:00.001-07:00

This example is very similar to the previous one where I showed you how to write an example using the YesNo MessageBox. Here the only difference is that the MessageBox is with the AbortRetryIgnore Button.

Ok, now I will proceed to write a small example of this. Basicly what I want to do here is to distinguish between the three different types of buttons that this type of MessageBox contains. Here I will use a swith statment because I find it a little more correct.
So the complete C# code is this:

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

private void button1_Click(object sender, EventArgs e)

{

DialogResult result;

result = MessageBox.Show("The Cd drive is not ready. \nReinsert and try again!", "Error on Drive", MessageBoxButtons.AbortRetryIgnore, MessageBoxIcon.Error);

switch (result)

{

case DialogResult.Abort:

MessageBox.Show("Abort Selected");

break;

case DialogResult.Retry:

MessageBox.Show("Retry Selected");

break;

case DialogResult.Ignore:

MessageBox.Show("Ignore Selected");

break;

default:

break;

}

Result when executing:

MessageBox using YesNo Button

2008-06-27T19:52:00.000-07:00

With the previous post you could see that MessageBox class is very powerful and contains a lot of options for the static method Show. Now we will see in more detail how to implement the functionalities of a Dialog containing a YesNo Button.

When you give the user that option, it is obvious that the behavior of the Yes Button must be different from the No so you must set this.

Let's proceed to write an example. This C# code example has basicly 2 functions: when the Dialog popus up, the user must select between the Yes or No options. If the Yes is selected, the application exits. If the No button is clicked, a Dialog will appear. So here is the code:

private void button1_Click(object sender, EventArgs e)
{
DialogResult result;
result = MessageBox.Show("Are you sure you want to exit?", "Application 1", MessageBoxButtons.YesNo);

if (result == DialogResult.No) {
MessageBox.Show("App won´t close");
}

if (result == DialogResult.Yes) {
this.Dispose();
}
}

If there are more options that the user can choose from, a switch statment could be a better option:

witch (result)
{

case DialogResult.No:
MessageBox.Show("App won´t close");
break;

case DialogResult.Yes:
this.Dispose();
break;

default:
break;

}

Result when executing:

MessageBox Tuning in C#

2008-06-27T12:23:00.000-07:00

MessageBox class is used when you want to show some kind of information or when the application needs user intervention.
This class contains static methods that help to interactuate with users. All you have to do is set the correct parameters of the show method. Some are: title, a proper message, icons, botons, quantities and more.

The show method returns a DialogResult type value that will need to be evaluated in order to make future actions, for example, open another dialog window.

Let’s look at some examples now:

I´ll start by creating a Windows From. Next, I´ll add 5 Buttons controls to the form and create a click event for all of them. On the click event method I created different messageBoxs for each one. Let’s analize them:

-For the button0, the code line is:

MessageBox.Show(this, "Hello", "Title Button0");

Nothing really complicated here. This creates a simple dialog with the text Hello, owner this and title Title Button0.

-For the button1, the code line is:

MessageBox.Show("Abort, Retry, Ignore example", "Title 1", MessageBoxButtons.AbortRetryIgnore);

This is a little more interesting. We indicated here that the title would be Title 1, the message Abort, Retry, Ignore example and the Button for this specific dialog is the AbortRetryIgnore Button, the same one you see in most windows applications.

-For the button2, the code line is:

MessageBox.Show(this, "Error on button2, Continue?" , "Title2", MessageBoxButtons.YesNo , MessageBoxIcon.Error);

This is very similar to the previus one: Owner this, title Title2, message Error on button2, Continue? , Button YesNo and Icon Error. This will create a dialog that contains both options Yes and No, and also an Error Icon located left of the message will appear.

-For the button3, the code line is:

MessageBox.Show("Warning", "Button3 Title", MessageBoxButtons.OK, MessageBoxIcon.Warning);

Similar to the others but now the Button is the Ok button and the Icon Warning will apear. So the purpose of this is to indicate an error, warning or a message that the user must see and give the only option of clicking the OK button.

-For the button4, the code line is:

MessageBox.Show(this, "Warning", "Button4 title", MessageBoxButtons.RetryCancel, MessageBoxIcon.Asterisk, MessageBoxDefaultButton.Button3);

Here the Button is the usual RetryCancel, the Icon Asterisk and the DefautlButton indicated to Button3. This defines the constat button.

Writing Registry keys

2008-06-19T08:54:00.000-07:00

We saw before how to read a registry key. Writing is similar and also accomplished by the RegistryKey object. C# .Net provides very easy methods under this object to write keys.

Be aware that the registry is a key part of an Operating System so you should know exactly what you are doing before actually doing it. Check every single line of the code written. On this example I’ll show you below, I will create a couple of keys with its proper folder too. By doing this I can be sure that any other registry key would be overwritten.

Take a look now at this example:

using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.Win32;

namespace WritingRegKeys
{
class Program
{
static void Main(string[] args)
{

RegistryKey RegKeyWrite = Registry.CurrentUser;
RegKeyWrite = RegKeyWrite.CreateSubKey
("Software\\MySoftware\\SubKeys");
RegKeyWrite.SetValue("Try", "True");
RegKeyWrite.SetValue("NumberValue", 1);

RegKeyWrite.Close();

RegistryKey RegKeyRead = Registry.CurrentUser;
RegKeyRead = RegKeyRead.OpenSubKey("Software\\MySoftware\\SubKeys");
Object regTry = RegKeyRead.GetValue("Try");
Object regNumber = RegKeyRead.GetValue("NumberValue");
RegKeyRead.Close();
Console.WriteLine("Try value: " + (String)regTry + " - - NumberValue: " + regNumber);

}
}
}

You can see that after creating the RegistryKey object I also created a subkey with the CreateSubKey method. This will generate another “subfolder” under MySoftware.

The Complete root is: HKEY_CURRENT_USER\Software\MySoftware\SubKeys.

With the RegKeyWrite.SetValue you have to specify the name of that key and the actual values you want to be stored. You can see that the fist value to be stored is a String and the second a Numeric value.

You can try this by reading the keys created above. That why the RegKeyRead Object is also created. Then we just open the SubKey and ask the values for the Try key and the NumberValue key. Run the code and the Console should look something like this:

When you execute the code, a new registry should be created. So let’s take a look at the registry to see if this is true. Open regedit to see the changes.

Accessing the Registry for reading keys in C#

2008-06-07T10:45:00.000-07:00

C# contains class object that make the job of manipulating the registry very easy.
Also, the registry is indexed that make much faster the reading job.

Ok, let’s now proceed to read from the registry.
First you need to make the import of the Microsoft.Win32 namespace that contains the registry access functions.
The second important thing you need to use RegistryKey object to make the actual reading.

Let’s now write a small piece of code to see how this works.

using System;
using System.Text;
using Microsoft.Win32;

namespace RegRead
{

class Program
{

static void Main(string[] args)
{

//Example 1
RegistryKey RegKey = Registry.LocalMachine;
RegKey = RegKey.OpenSubKey(
"HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\1");
Object cpuName = RegKey.GetValue("ProcessorNameString");
Console.WriteLine("Your CPU name is:" + cpuName);

Console.WriteLine("");

//Example 2
RegistryKey RegKey2 = Registry.CurrentUser;
RegKey2 = RegKey2.OpenSubKey("Printers");
Object printerName = RegKey2.GetValue("DeviceOld");
Console.WriteLine("Your Printer name is: " + printerName);

Console.Read();
}
}
}

The first thing you need to do is to import the Microsoft.Win32 namespace.
Then, if you look at the definition of the instance of the RegistryKey object, you will see that it is pointing to Local Machine, which means that the HKEY_LOCAL_MACHINE folder will be enable for reading.
(To open the Registry editor just go to start->Run: regedit).
After this step, we simple need to find the folders/subfolders where the key is located and read it.

The second example is pretty much the same. The only major difference is that the
HKEY_CURRENT_USER folder will be available.

Advance C# programming, overload unary plus.

2008-05-30T15:27:00.000-07:00

C# let’s you overload the behaviour of some unary operator such as: unary plus, minus, prefix increment, decrement, true keyword, false keyword and more.

Ok, now let’s make a small example on how to overload the unary plus. For this, you need to define a method (in the class that you want to implement the overload) containing a few things: the return type, the operator keywords (in this case +), the parameter that usually is the object or structure where the method is being defined.

Let’s make now a small example:

-First we create a small class and define the overload plus:

public class MyClass
{
public double value;

public static MyClass operator +(MyClass Mc)

{
MyClass myC = new MyClass();
if (Mc.value <0)
myC.value = -Mc.value;
else
myC.value = Mc.value;

return myC;
}

}

-Main:

static void Main(string[] args)
{

MyClass MyCs = new MyClass();
MyClass MyCsP = new MyClass();

//Both negative and positive values to see effect
MyCs.value = -10.80;
MyCsP.value = 300;

Console.WriteLine("Before: " + MyCs.value);
Console.WriteLine("\t" + MyCsP.value);

//Using the + operator triggers the method
MyCs = +MyCs;
MyCsP = +MyCsP;

Console.WriteLine("After: " + MyCs.value);
Console.WriteLine("\t" + MyCsP.value);

Console.Read();

}

-Console:

MouseDown Event in C#.

2008-05-19T16:23:00.000-07:00

The MouseDown event is the one I personally use every time a control needs both events for left and right click (middle click is also supported).
So lest say we want to add the mouseDown event to a Button control somewhere in a windows form. So you can go ahead and add this event.

This header shows appear in the form:

private void button2_MouseDown(object sender, MouseEventArgs e)

So lets proceed to add some code here.
The way to see which button has been clicked is by using a switch statement:

switch (e.Button)
{
case MouseButtons.Left:

//Place here event for left click

break;

case MouseButtons.Right:

//Place here event for right click

break;

default:

break;

}

Great, now your application can distinguish between lest and right click.
To make sure this works, you can add a messageBox saying what event should run.

Complete Code:

private void button2_MouseDown(object sender, MouseEventArgs e)
{
switch (e.Button)
{
case MouseButtons.Left:

MessageBox.Show(this, "Left Button Click");

break;

case MouseButtons.Right:

MessageBox.Show(this, "Right Button Click");

break;

default:

break;

}
}

Creating Tooltip to Button Control from scratch

2008-05-07T10:19:00.000-07:00

First of all, start by creating a new Windows form application in Visual Studio 2005. (You can download the Express Edition clicking the link on My Links section).

After that, place a Button Control somewhere in the form as you see below:

Ok, now we can proceed to add the tooltip event to the button1. This is actually very easy. I will show you the way I use for doing this.

Navigate through the toolbox until you find the tooltip control. Grab the control and place it somewhere in the form.

You will see that the Control is placed in a bar below the form. Also the Tooltip Control is created with the name tooltip1. Ok, now let’s add some event and write a few code lines.

Click the button1 and under properties double click the MouseHover event. This creates the method that we use for the tooltip control. Now in the method body add this line of code:

toolTip1.SetToolTip(button1, "Information for Button1");

Great, now run the app and see what happens. It should look something like this:

Some other cool features on this C# Control:
- toolTip1.IsBalloon = true;
(Converts to a ballon window)

- toolTip1.ToolTipIcon = ToolTipIcon.Error;
(Assign icon to the tooltip)

- toolTip1.ToolTipTitle = "This is the Title";
(Assigns a title)

Complete Code:

private void button1_MouseHover(object sender, EventArgs e)
{
toolTip1.SetToolTip(button1, "Information for Button1");
toolTip1.IsBalloon = true;
toolTip1.ToolTipIcon = ToolTipIcon.Error;
toolTip1.ToolTipTitle = "This is the Title";
}

Deleting elements from a list while iterating

2008-04-28T08:33:00.000-07:00

In C# you are not allowed to iterate and delete elements from a list at the same time. So what you need to do is to find a way to delete these elements later, after knowing what you are going to eliminate. In C++ you won’t have this problem but in C# an exception will be triggered.

This example below demonstrates how to solve this nicely. Basically what it does is that looks for none existing files from your hard drive and saves these on a separate List. Suppose that the object Element contains a string value representing a file path:

public void validateList() {

//New list that will contain the Objects to be deleted later on.
List<Element> listToDelete = new List<Element>();

//ListAll contains all the Element objects
foreach (Element e in listAll()) {
string location = e.loc;
if(!File.Exists(location)){
listToDelete.Add(e);
}

}
foreach (Element e in listToDelete) {
listAll.Remove(e);
}

}

Text file Reading and Writing in C#

2008-04-20T11:01:00.000-07:00

This program below demonstrates the use of StreamWriter and StreamReader (both derive form the abstract type TextWriter and TextReader respectively). The .Net Framework has simple solutions to work with files. When working with text files there are usually three common steps:

1- Opening the file
2- Reading/Writing
3- Closing it

Now, lets take a look at this example:

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;

namespace ConsoleApplication
{
class Program
{

public static void Main(string[] args)
{

//C# Code for writing into a file we call: File.txt

FileInfo f = new FileInfo("File.txt");
StreamWriter Text = f.CreateText();

//Insert text in separate lines
Text.WriteLine("-->Line One content");
Text.WriteLine("--->Line Two Content");

//Insert text but does not create a new line
Text.Write("---->Line Three ");
Text.WriteLine("Content");

//To create new Line.
Text.Write(Text.NewLine);
Text.WriteLine(System.DateTime.Now);
Text.Close();

//Calling the method to read File.txt
readFiles();

Console.Read();

}

public static void readFiles()

{

//We open File.txt
StreamReader sr = new StreamReader("File.txt");
string lines = null;

//Here we do a while loop in order to look for none empty lines.
while ((lines = sr.ReadLine()) != null)
{
Console.WriteLine(lines);
}

sr.Close();
}

}
}

Connection to a data source in C#

2008-04-10T09:05:00.000-07:00

Here is an easy way to get access for example, to an Access database located in your program folder using ADO .NET .

//Add this namespace for database handle
using System.Data.OleDb;

public OleDbConnection GetConnection()
{

OleDbConnection acc = new OleDbConnection();
conn.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=db.mdb";

return acc;

}

Later, when you want to open the database to load, save or whatever you need to do you can use the sentence, being Instance() a method used by Singleton pattern and ConnectionMgr the class name for managing connections:

IDbConnection acc = ConnectionMgr.Instance().GetConnection();

Convert Icon to Image in C#

2008-04-10T09:04:00.000-07:00

This is actually very easy since we can use methods provided by the framework.So let’s write an example of how easy this is.

Icon a = new Icon(location);//location can be a string pointing to a file in your hard drive

Image im = a.ToBitmap();

The continue and goto statements.

2008-04-01T10:18:00.000-07:00

The continue statement basically what is does is that it return controls to the boolean expressing that controls an iteration statement. Example:

for (int i = -6; i != 0; i++)
{
if (i == -3)
{
continue;
}
Console.WriteLine("i value: " + i);
}

So when the continue statement is executed under the if condition, it tells the for iteration to continue to the next iteration, and because of this the value -3 does not appear in the console.

The Continue statement is commonly used in while, do, for, switch and foreach statements.

The goto statement is very useful when you need to unconditionally transfer control to a labelled statements. In C# to make a labels statement is very easy, just place a name for the labelled followed by “:” on any statement. Example:

for (int j = 0; j != 7; j++)
{
Console.WriteLine("j value: " + j);
if (j == 4)
{
goto Exit;
}
}
Exit: Console.WriteLine("Exit reached, loop finished");

You can also use it in a switch statement by writing for example, “goto case 2”.