SOURCE CODE

C# - Variables

A variable is nothing but a name given to a storage area that our programs can manipulate. Each variable in C# has a specific type, which determines the size and layout of the variable's memory the range of values that can be stored within that memory and the set of operations that can be applied to the variable.

The basic value types provided in C# can be categorized as −

Type	Example
Integral types	sbyte, byte, short, ushort, int, uint, long, ulong, and char
Floating point types	float and double
Decimal types	decimal
Boolean types	true or false values, as assigned
Nullable types	Nullable data types

C# also allows defining other value types of variable such as enum and reference types of variables such as class, which we will cover in subsequent chapters.

Defining Variables

Syntax for variable definition in C# is −

Here, data_type must be a valid C# data type including char, int, float, double, or any user-defined data type, and variable_list may consist of one or more identifier names separated by commas.

Some valid variable definitions are shown here −

int i, j, k;
char c, ch;
float f, salary;
double d;

You can initialize a variable at the time of definition as −

int i = 100;

Initializing Variables

Variables are initialized (assigned a value) with an equal sign followed by a constant expression. The general form of initialization is −

variable_name = value;

Variables can be initialized in their declaration. The initializer consists of an

equal sign followed by a constant expression as −

  = value;

Some examples are −

int d = 3, f = 5;    /* initializing d and f. */
byte z = 22;         /* initializes z. */
double pi = 3.14159; /* declares an approximation of pi. */
char x = 'x';        /* the variable x has the value 'x'. */

It is a good programming practice to initialize variables properly, otherwise sometimes program may produce unexpected result.

Library Management Program in C#

class Program
{
static public int[] student = new int[100];
static public int[] i = new int[5];
static public int[] b = new int[5];
static public int issuelimit = 2;
static public string bookname;
static public int id;
static public int bookcount;
static public int bookid;
static public int choice=0;
static public char Repeat;

static void Main(string[] args)
{
int choice=1;
Console.WriteLine(" What do u want to do?\n");
Console.WriteLine("1.Add a book to the Library");
Console.WriteLine("2.Register a user ");
Console.WriteLine("3.Issue a book");
Console.WriteLine("4.Display list of Registered user");
Console.WriteLine("5.Display list of books in library");
Console.WriteLine("6.Exit");

choice = Convert.ToInt16(Console.ReadLine());

LibMng lb = new LibMng();
switch (choice)
{
case 1:
{
do
{
Console.WriteLine("Enter the name of the book and the author's name: ");
string bookname = Convert.ToString(Console.ReadLine());
string author = Convert.ToString(Console.ReadLine());
bookcount++;
bookid++;
Console.WriteLine("\nDo you wish return more from the same card??(y/n)");
Repeat = Convert.ToChar(Console.ReadLine());
}
while (Repeat == 'y' || Repeat == 'Y');
break;
}
case 2:
{
Console.WriteLine("Enter the name and address of user: ");
string studentname = Convert.ToString(Console.ReadLine());
string studentadd = Convert.ToString(Console.ReadLine());
Console.WriteLine("Enter the card ID");
id = Convert.ToInt16(Console.ReadLine());
do
{
if (student[id] != 0)
{
lb.bookReturn();
}
else
{
Console.WriteLine("Till no book is issued to this card");
break;
}
Console.WriteLine("\nDo you wish return more from the same card??(y/n)");
Repeat = Convert.ToChar(Console.ReadLine());
}
while (Repeat == 'y' || Repeat == 'Y');
break;
}
case 3:
{
Console.WriteLine("Enter the Student id");
id = Convert.ToInt16(Console.ReadLine());
do
{
if (student[id] < 2)
{
lb.Issue();
}
else
{
Console.WriteLine("Sorry no more books can be issued");
break;
}

Console.WriteLine("\nDo you wish to issue more to the same card??(y/n)");
Repeat = Convert.ToChar(Console.ReadLine());
}
while (Repeat == 'y' || Repeat == 'Y');
break;
}
case 4:
{
do
{
Console.WriteLine("the list of registered student is:");
foreach (int a in Student)
{
Console.WriteLine("Name: ", a.studentname);
Console.WriteLine("StudentId: {0}", a.studentid);
Console.WriteLine("Number of books issued: {0}", a.NoOfBooksIssues);
}
Console.WriteLine("do you wish to continue??(y/n)");

} while (Repeat == 'y' || Repeat == 'Y');
break;
}
case 5:
{
do
{
Console.WriteLine("the list of books in library:");
foreach (int b in BookLibrary)
{
Console.WriteLine("Book Title: {0}", b.bookname);
Console.WriteLine("Book Id: {0}", b.bookid);
Console.WriteLine("Author name: {0}", b.author);
}
Console.WriteLine("do you wish to continue??(y/n)");

} while (Repeat == 'y' || Repeat == 'Y');
break;
}
case 6:
{
break;
}

}
Console.ReadLine();
}
}
class LibMng : Program
{
public void Issue()
{
Console.WriteLine("Enter The Book id ");
int reqbook = Convert.ToInt32(Console.ReadLine());
if (reqbook == bookid)
{
if (i[0] != 0)
{
i[0]--;
Console.WriteLine("The Book is issued to Card{0}", id);
student[id]++;
}
else
Console.WriteLine("Book is not available");
}
}
public void display()
{
Console.WriteLine("the books taken are: ");
}

public void chckAvail()
{
Console.WriteLine("Enter The Book id");
int req = Convert.ToInt32(Console.ReadLine());
if (req == bookid)
{
if (i[0] != 0)
{
Console.WriteLine("The number of copy of the Book is::{0}", i[0]);
}
else
Console.WriteLine("Book is not available");
}
}
}

class BookLibrary: Program
{
public int bookcount;
public int bookid;
public string bookname;
public string booktitle;

public BookLibrary(int bookcount, int bookid, string bookname, string booktitle)
{
this.bookcount = bookcount;
this.bookid = bookid;
this.bookname = bookname;
this.booktitle = booktitle;
}

}
class Student
{
public int studentcount;
public int studentid;
public string studentname;
public int noOfbookissues = 0;

public Student(int studentcount, int studentid, string studentname, int noOfbooksissued)
{
this.studentcount = studentcount;
this.studentid = studentid;
this.studentname = studentname;
this.noOfbookissues = noOfbookissues;
}
}
class IssueReturn: Program
{
public void bookReturn()
{
Console.WriteLine("Enter The Book ID");
int req1 = Convert.ToInt32(Console.ReadLine());

if (req1==bookid)
{
if (i[0] != 1)
{
i[0]++;
Console.WriteLine("The Book is returned from Card {0}", id);
student[id]--;
}
else
Console.WriteLine("Till the Book is not issued to this Card");
}
}
}
}
}

How to SUM two fields within an SQL query

Value1 Value2
-----------------------
3 6
1 5
4 3
8 1

SQL Query :

select Value1 + Value2 as qty from Table1;

Result :

qty
---------
9
6
7
9

How to Convert Amount (Currency) in words directly on Crystal Report.

To Create function follow the steps given below:
(i) go to Field Explorer
(ii) right click on Formula Fields click on New give specific name
(iii) Formula Editor window will open just paste the Code given below
(iv) Save & Close...
(v) Just drag the Field to your specific required Location that done...

Changes to be made from your side is
i) AmntTypes.UnitCost : This is a Database Field. Change as per your requirement.

Please note if you have Currency as Datatype in SQL DB than Do use ToNumber() function to convert it to number otherwise it will throw error of Number Required.

numbervar RmVal:=0;
currencyVar Amt:=0;
numbervar pAmt:=0;
stringvar InWords :="Rupees ";

Amt := ({AmntTypes.UnitCost});

if Amt > 10000000 then RmVal := truncate(ToNumber(Amt)/10000000);
if Amt = 10000000 then RmVal := 1;
if RmVal = 1 then
InWords := InWords + " " + towords(RmVal,0) + " crore"
else
if RmVal > 1 then InWords := InWords + " " + towords(RmVal,0) + " crores";

Amt := Amt - Rmval * 10000000;
if Amt > 100000 then RmVal := truncate(ToNumber(Amt)/100000);
if Amt = 100000 then RmVal := 1;
if RmVal >=1 then
InWords := InWords + " " + towords(RmVal,0) + " lakhs";

Amt := Amt - Rmval * 100000;
if Amt > 0 then InWords := InWords + " " + towords(truncate(Amt),0);
pAmt := (ToNumber(Amt) - truncate(ToNumber(Amt))) * 100;
if pAmt > 0 then
InWords := InWords + " and " + towords(pAmt,0) + " paisa only"
else
InWords := InWords + " only";
UPPERCASE(InWords)