Differences between Struct And Class

Structs are value types.
classes are reference types.

A data type is a value type if it holds the data within its own memory allocation.
A reference type contains a pointer to another memory location that holds the data.

Value Types
-------------
Value types include the following:
All numeric data types
Boolean, Char, and Date
All structures, even if their members are reference types
Enumerations, since their underlying type is always SByte, Short,
Integer, Long, Byte, UShort, UInteger, or ULong

Reference Types
-----------------
Reference types include the following:
String
All arrays, even if their elements are value types
Class types, such as Form
Delegates

class Program
{
 static void Main(string[] args)
 {
  #region Reference type Class
   productInfo pinfo1 = new productInfo();
   productInfo pinfo2 = new productInfo();
   pinfo1.productName = "Product One";            
   pinfo2 = pinfo1;
   Console.WriteLine("pinfo1.productName :" + pinfo1.productName);
   Console.WriteLine("pinfo2.productName :" + pinfo2.productName);
   pinfo2.productName = "Product Two";
   Console.WriteLine("pinfo1.productName :" + pinfo1.productName);
   Console.WriteLine("pinfo2.productName :" + pinfo2.productName);
  #endregion            

  Console.WriteLine("--------------------------------");

  #region Value type Struct
   customerInfo cus1 = new customerInfo();
   customerInfo cus2 = new customerInfo();
   cus1.customerName = "Customer One";
   cus2 = cus1;    
   Console.WriteLine("cus1.customerName :" + cus1.customerName);
   Console.WriteLine("cus2.customerName :" + cus2.customerName);
   cus2.customerName = "Customer Two";
   Console.WriteLine("cus1.customerName :" + cus1.customerName);
   Console.WriteLine("cus2.customerName :" + cus2.customerName);
  #endregion

  Console.Read();
 }
}

public class productInfo
{
 private string _productName;
 public string productName
 {
  get { return _productName; }
  set { _productName = value; }
 }
}

public struct customerInfo
{
 private string _customerName;
 public string customerName
 {
  get { return _customerName; }
  set { _customerName = value; }
 }
}

Output Value is :
pinfo1.productName :Product One
pinfo2.productName :Product One
pinfo1.productName :Product Two
pinfo2.productName :Product Two
--------------------------------
cus1.customerName :Customer One
cus2.customerName :Customer One
cus1.customerName :Customer One
cus2.customerName :Customer Two





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Microsoft SQL IDENTITY

When you want to get auto-generated ID value from table which you make inserting data at the same time, you can make two ways. One of the ways to meet this requirement is using Sql Identity and @@Identity keyword. Second ways is using NEWID() keyword.

Firstly you need to create table like that ...

CREATE TABLE Customer
(
CustomerID INT IDENTITY(1, 1) NOT NULL,
CustomerName VARCHAR(25) NULL,
PhoneNo VARCHAR(20) NULL
)

Then, you need to make storeprocedure ....

CREATE PROCEDURE getCustomerIDAfterInsertCustomer
@CustomerID INT = NULL OUTPUT,
@CustomerName VARCHAR(25),
@PhoneNo VARCHAR(20)
AS
BEGIN
INSERT INTO Customer (CustomerName, PhoneNo) VALUES (@CustomerName, @PhoneNo)
SET @CustomerID = @@IDENTITY
SELECT @CustomerID AS CustomerID
END

Then, execute procedure like that ...

DECLARE @CustomerID AS INT
EXEC getCustomerIDAfterInsertCustomer @CustomerID OUTPUT, 'Customer 1', '654-9956213'

If you make delete this table, you will also need to make reindex, so you should do like that ....

DELETE FROM Customer
DBCC CHECKIDENT(Customer, RESEED, 0)

Way to use c# datetime.

When you want to get number of days according to given date,
you can use this function in c# .net

public int getNumberOfDayByGivenDate(DateTime dtGivenDate)
{
DateTime dtMyDate = DateTime.Parse("16/10/2009");
TimeSpan tsGetNumber = dtGivenDate.Subtract(dtMyDate);
return tsGetNumber.Days;
}

When you want to get date format data according to given integer number,
you can use below function in c# .net

public DateTime getDateByGivenNumber(int GivenNumber)
{
DateTime dtMyDate = DateTime.Parse("16/10/2009");
TimeSpan tsByGivenNumber = new TimeSpan(GivenNumber, 0, 0, 0);
return dtMyDate.Add(tsByGivenNumber);
}