Narrowing and widening
If you know what casting is, this will be easy for you
A byte is a small integer that has a maximum value of 255, if you want to save 315 in that byte variable, you will need to widen it to an integer for example.
Archive for the ‘02 – C# intro’ Category
Narrowing and widening
Sunday, March 8th, 2009Date And Time data types
Sunday, March 8th, 2009This one is so not important at this strange, i will come back to it.
Dealing with Simple Strings
Sunday, March 8th, 2009From before, you know how to declare a string, here it is again for you
string myString;
myString = “Hi There, i am a string”;
Parsing
Assuming your string is
string myStringInteger = “10″;
and you want to get that value in an integer variable
You can simply use the parse keyword
int myInteger = int.Parse(myStringInteger);
You can do that to a boolean variable as well
string myBoolString = “True”;
bool myBool = bool.Parse(myBoolString);
Strings come with extra functionality as well.
myBoolString.Length will be equal to 4 since True has 4 letters.
Strings are no good for efficiency, rather you would want to use StringBuilder for larger texts
You may also be interested in knowing that although a string is not a value type, the == operator is overloaded to mean “Is the content identical in both strings”, If you don’t know why this is strange, You will find out as you read
Declaring Varibles
Sunday, March 8th, 2009Declaring variables in C#
Here i am not talking about arrays or more complex structures, the basic variable declaration and initialization is as follows
Lines that start with // are not for the compiler, they are comments and effectivly ignored on compile
//Declare an integer
int myInteger;
//Give it initial value
myInteger = 15;
//Declare and Initialize @ once
int myOtherInteger = 16;
//Declare More than 1 variable at once
int var1, var2, var3;
//More on one line, Declare and initialize many
int var4 = 45, var5 = 46, var6 = 47;
Surely you can replace int with float or string or bool or any other.
Console Output with Console.WriteLine
Sunday, March 8th, 2009So, you have already used this
But for the most part of this text we will use the functionality from System.Console class to display the output of our programs
Console.WriteLine(“A string”);
prints A string, if you want to print variables
Console.WriteLine(“Var1 {0} Var2: {1} Var4: {3} Var3: {2}”, var1, var2, var3, var4);
this will print the variables within the string, notice that Var4 and Var3 are reversed in the string, the variables takes the indexes 0, 1, 2, 3… you can use {0} more than once to print variable var1 more than once.
On a relevant note, Console.WriteLine will print the string on a new string, if you do not want that you can use Console.Write in the same way
C# rules – Starting C#
Sunday, March 8th, 2009Ok, here is a quick intro to the language
1- C# is case sensitive, so myVariable is not the same as MyVariable
2- The entry point of the program by default returns void (You can change that into an integer if you insist on your program returning a zero for ok or an error code), it takes string[] args as parameter so that you can pass the program command line arguments
3- No globals
4- Command line arguments will be in the array, you can then foreach around them (Or use a for loop) to extract them
5- You can use GetCommandLineArgs() to get the array we talked about in 4, this method is static, you can learn what static is later
Will add things here as suitable as i go.
Your first C# program
Sunday, March 8th, 2009To start, open your MSVS express (Free) or Pro
Go to File -> New -> Project
Chose Console Application from the icons that appear
Name your project HelloWorld
—-
You will see MSVS creating a new file for you named “Program.cs”, and in that file you should see something like.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace HelloWorld
{
class Program
{
static void Main(string[] args)
{
}
}
}
Already we have a namespace (Same as project name), a Program Class,
and a program entry point that is always named Main.
So, Add the following line to your Main (Between the currly brackets)
Console.WriteLine(“HelloWorld”);
Console.ReadLine();
Now go to the build menu, and then to Build Solution
Now navigate to your Documents directory, In my case on Windows Vista it is
C:\Users\yazeed\Documents\Visual Studio 2008\Projects\HelloWorld\HelloWorld\bin\Debug
and double click HelloWorld.exe
bravo, you are done with your first C# program….
the C# compiler on the command line
Sunday, March 8th, 2009You actually get the compiler when you download the .NET framework and not the Visual Studio.
You can run the compiler from the command line, So assuming you have a very simple program in myprog.cs and you want to compile it with the command line compiler, you can compile it at the command line like this.
csc /target:exe myprog.cs
there are pleanty of compiler flags and you even need to include the names of the files you want to make use of in your program, so why not skip this one and use the Microsoft IDE.
i will come back here and give you all the command line arguments and everything some time later, for now i am not using this, it involves more typing than the progam itself.