C# tutorial-Database support: Connection object

C# Database Access with ADO.NET


ADO.NET is the evolution of ADO (Active Data Objects). It is used to interact with a database or a data source. ADO.NET contains such useful classes to work with the databases as:

Connection
Command
DataReader
DataSet
DataAdapter

Connection Object

When you want to connect to a database, you will use the Connection object. In this part you will learn to connect to databases of Ms. Access and SQL Server. To connect to Ms. Access databases, we use System.Data.Oledb class. And to connect to SQL Server databases, we use System.Data.SqlClient class.

 

Example: Connect to Ms. Access database

OleDbConnection cn;

//Create Connection object

 

cn = new OleDbConnection("Provider=Microsoft.Jet.Oledb.4.0; Data Source=" + Application.StartupPath + "\\dbimages.mdb");

'Open Connection to the database

cn.Open();

OR

//Create Connection object

OleDbConnection cn=new OleDbConnection();

            //Set connection string

   cn.ConnectionString="Provider=Microsoft.Jet.Oledb.4.0; Data Source="+ Application.StartupPath+ "\\dbimages.mdb";

cn.Open();

 

This code will connect to Ms. Access database “dbimages.mdb” located in start up path of the current project. The database contains a table named tblimages that store image ID and its path.

 

Example: Connect to SQL Server database

 

SqlConnection cn;

//Create Connection object

cn = new SqlConnection("Server=(local); Database=dbimages; User=sa; Password=123;");

//Open connection

cn.Open();

 

OR

//Create Connection object

SqlConnection cn=new SqlConnection();

//Set connection string

cn.ConnectionString="Server=(local); Database=dbimages; User=sa; Password=123;"

//Open connection

cn.Open();

 

This code will connect to SQL Server database “dbimages” in the local machine.


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comment

Posted comments

Phan Neth, CICI, year 3:

Now it is ok teacher. I can connect to database and select data from it. Than you so much teacher !!!!!

04-30-2013

Dara:

Copy and paste the link below to the address box to learn how to connect C and Mysql server:
http://www.worldbestlearningcenter.com/index_files/cpp-tutorial-connect_mysql_database.htm

04-27-2013

Phan Neth, CICI, year 3:

Hello teacher i want to connect C programming language to MySql server but it have problem. When i compile it always error with library " my_global.h
and mysql.h", so how should i do?

04-27-2013

Phan Neth, Year 3 at CICI,:

I have some problem about connection to mysql server. So I hope teacher can help me. Thank !!!!

04-26-2013

Federico:

Output appears the same also this way:

static void Main(string[] args)
{
int[,] myArray = new int[5, 5];
int row, i;
int n = 1;

for (row = 0; row < 5; row++)
{
for (i = 0; i < 5; i++)
{
myArray[row, i] = n;
if (row == 1 && i == 2) Console.Write(" \t");
else Console.Write("{0} \t", n);

if (n!=26) n++;
if((i+1)%5==0) Console.WriteLine("\n");
}
}
Console.ReadLine();
}

04-13-2013

Dara:

Let pointer p point to the index 1 elem (value=2) of the array.
int *p= a+1;
Let pointer q point to the index 6 elem (value=5) of the array.
int *q= a+6;
-Expression q-p is the subtraction of address of the index 6 element and the address of index 1 elem of the array. So, the result is 5.
-Expression *p+*q is the sum of the value of index 1 elem (2) and the value of index 6 elem (5). So, the result is 7.
In conclusion, the output is 57.

03-28-2013

Anushka :

Find the output of following code
main()
{
int a[] = {1,2,9,8,6,3,5,7,8,9};
int *p= a+1; int *q= a+6;
cout<< q-p <<*p+*q; }

03-28-2013

Dara:

Option Explicit
Dim Cn as New ADODB.Connection
Private Sub_Form_Load()
Cn.Open "Provider=SQLOLEDB; Data Source=ServerName; Initial Catalog=DatabaseName;UserID=UserName; Password=Passw"
End Sub
You will need to replace ServerName with the name of your server (installed SQL Server), DatabaseName withe the name of your data file that you want to connect to, UserName with the name of the user to login to SQL Server, and Passw with the password used to login to SQL Server.

03-13-2013

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