How to use MySql With C#
Ross Sherman
1
Using MySql
MySql is free. You could download it from:
http://dev.mysql.com/downloads/
When the setup wizard completes check Launch the MySQL Instance
Configuration Wizard and click Finish
Choose Development Machine and leave the defaults as they are
Choose a password
Add at least one user account
Choose defaults for the rest of the screens
Once installed, start the MySQL Workbench; click Open Connection
to Start Querying
Creating a new database in MySql; creating new tables in the database
create database videostore;
use videostore;
create table moviesrented
(personid int(4),
movieid int(4)
);
create table customer (id int(4),
lastname varchar(12), firstname varchar(12),
email varchar(12),
pass varchar(12)
);
create table movies
(id int(4),
moviename varchar(20),
numberavailable int (3));
From Professor Gueorguieva’s database
lecture:
SQL Server
Data Type
Corresponding C# or .NET
Framework
Data Type
bit
bool
datetime
dateTime
decimal
decimal
float
double
int
int
money
decimal
nchar
string
nvarchar
string
Inserting values into your database’s tables
INSERT INTO customer
VALUES ('1212','Stan','Gundy','stan@hotmail.com','coach'),
('1132','Phil','Jackson','phil@hotmail.com','eleven');
INSERT INTO movies
VALUES ('1333','Mission_Impossible','3'),
('1334','Jack_Reacher','4'),
('1335','Admission', '2');
INSERT INTO moviesrented
VALUES ('1212','1334'),
('1212','1335'),
('1132','1334');
Querying your database
Select *
from customer;
select max(id)
from customer;
select id
from movies
where id = 1212;
select *
from customer
where firstname like ‘P%’;
select customer.id as IDNameCustID, customer.firstname, moviesrented.persionid, movies.moviename
from moviesrented, customer, movies
where moviesrented.persionid = customer.id
and moviesrented.movieid = movies.id;
Deleting rows, dropping tables, and adding
columns
To delete a row in a table:
delete
from moviesrented
where movieid = 1212;
To delete all rows from a table:
delete
from moviesrented;
To drop a table from your database:
drop table moviesrented;
To add a new column to an existing table:
alter table
customer
add birthdate date;
If you run into a problem deleting rows:
1) You might run into a problem when you
try to delete rows. To fix this problem go to
the Edit tab in the MySql Workbench and
click on preferences.
2) Once you have clicked on preferences, click on SQL
Queries and make sure that “Safe Updates” is unchecked.
If it is checked, uncheck it, press ok, and restart MySql for
the change to take affect.
Connecting Visual Studio to
MySql:
First, Create a new Windows Forms
Project.
Next, you will need to add MySql.data as a reference.
Adding MySQL.data as a reference:
In the Solution Explorer, click on the name of your presentation, right click on
references, click on add reference.
9
After clicking on add reference you will be taken to the reference manager form.
In Reference Manager form, select Extensions, find MySql.Data and press the check
box next to MySq.Data, them click on ok.
At this point, you have created a database
and you have connected that database to
MySql.
Now, you need to query and manipulate the
data from your database in your C# code.
Go to the design section of your
newly created windows form
and add a button to it. Double
click the button to go to the
code.
11
At the top, include the line: using MySql.Data.MySqlClient;
In the button’s code include the following lines:
private void button1_Click(object sender, EventArgs e)
{
try
{
string connectionInfo = "datasource = localhost; port = 3306; username = root; password = csi";
MySqlConnection connect = new MySqlConnection(connectionInfo);
connect.Open();
MessageBox.Show("Connected");
connect.Close();
}
catch(Exception ex)
{
MessageBox.Show(ex.Message);
}
}
To find out what to put into:
string myConnection = "datasource = localhost; port = 3306; username = root; password = csi";
go to the MySql workbench and press ctrl+u.
The following screen should appear:
The password is the password you created. If you are using the school’s computer the password is csi.
How to use MySql to create a login.
1) Place two labels, two textboxes, and a button on your form.
2) Double click on the button to edit the code for the button.
In my code on the next slide:
FirstName’s textbox is textBox1 and Password’s
textbox is textBox2 (I renamed the text but not the
actual textboxes). The login button is button1.
Check the entered firstname and password with the customer
table of the videostore database.
private void button1_Click(object sender, EventArgs e)
{
try
{
string connectionInfo = "datasource = localhost; port = 3306; username = root;”
+ “password = csi";
MySqlConnection connect = new MySqlConnection(connectionInfo);
MySqlCommand SQLCommand1 = new MySqlCommand("select * from videostore.customer”
+ “where firstname = '"+ textBox1.Text +"‘”
+ “and pass = '"+ textBox2.Text +"';", connect);
MySqlDataReader reader;
connect.Open();
reader = SQLCommand1.ExecuteReader();
int count = 0;
while (reader.Read())
{
count = count + 1;
}
Login Button Code Continued
if (count == 1)
{
MessageBox.Show("Firstname and password is correct");
}
else if (count > 1)
{
MessageBox.Show("Duplicate Firstname and password. You are not allowed access");
}
else
MessageBox.Show("Firstname and password is not correct");
connect.Close();
} // end of try block
catch(Exception ex)
{
MessageBox.Show(ex.Message);
}
} // end of login button code
Adding additional forms to your Visual Studio project
First, right click on presentation. Then, go down to add and click on new item. Select windows form
and click add.
The code that makes clicking on the login button take
you to the second form.
Go back to the code for the login button in slide 17. Inside of if (count == 1) add the 3 lines of code
that are in purple:
if (count == 1)
{
MessageBox.Show("Firstname and password is correct");
this.Hide();
Form2 f2 = new Form2();
f2.ShowDialog();
}
Querying and inserting values into a database
First, add 4 labels, 4 textboxes, and a button to your second form.
Then double click on enter data and enter the following code to
find the largest id that any customer has:
private void button1_Click(object sender, EventArgs e)
{
string connectionInfo = "datasource = localhost; port = 3306;"
+ "username = root; password = pawsox11";
MySqlConnection connect = new MySqlConnection(connectionInfo);
MySqlCommand SQLCommand1 = new MySqlCommand(" select max(id) as 'id‘”
+ ” from videostore.customer;", connect);
MySqlDataReader reader;
connect.Open();
reader = SQLCommand1.ExecuteReader();
Querying and inserting values into a database continued
In the code below, you are adding one to the max(id) – the largest customer id – and you are inserting
that value, along with four copies of string k, into the customer table of the videostore database:
int id = 1;
while (reader.Read())
{
id = reader.GetInt32("id") + 1;
MessageBox.Show("This is" + id);
}
connect.Close();
string k = "stop";
MySqlCommand SQLCommand2 = new MySqlCommand("insert into”
+ ”videostore.customer(id,lastname,firstname,email,pass)"
+ "values('" + id + "','" + k + "','" + k + "', '" + k + "', '" + k + "');", connect);
connect.Open();
reader = SQLCommand2.ExecuteReader();
connect.Close();
} // close the enter data button code
Adding an exit button
Add a new button to the second form. Double click on the
button. Add the following code to the button:
Application.Exit();
Adding things to a list box from a database
Add a listbox and a new button to your second form. Double click on the new
button (I named the text of the button “put into list box” but the button’s name is
button2 – the exit button is button 3 in my code).
Adding things to a list box from a database continued
Because the scope of this button doesn’t include objects created in the other button in this
form you will have to create a new object of class MySqlConnection. In the code below I
gave the new object of class MySqlConnection the same name as it had in the other button:
connect. The SQL query in this code is the same SQL query that I introduced in slide 5.
private void button2_Click(object sender, EventArgs e)
{
string connectionInfo = "datasource = localhost; port = 3306;"
+ "username = root; password = pawsox11";
MySqlConnection connect = new MySqlConnection(connectionInfo);
MySqlCommand SQLCommand1 = new MySqlCommand("select * from ”
+ “videostore.customer as c,"
+ "videostore.moviesrented as mr,"
+ "videostore.movies as m where c.id =“
+ “mr.personid and m.id"
+ "= mr.movieid and c.firstname = "
+ "'" + textBox1.Text + "';", connect);
Adding things to a list box from a database continued
MySqlDataReader reader;
try
{
connect.Open();
reader = SQLCommand1.ExecuteReader();
while (reader.Read())
{
string movieName, firstNameinC;
int id = 1;
movieName = reader.GetString("moviename");
firstNameinC = reader.GetString("firstname");
id = reader.GetInt32("id");
listBox1.Items.Add(firstNameinC + " " + movieName + " " + id);
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
} // end of button2’s code
Previously, I have shown
you how an object of the
class MySqlDataReader (I
named the object reader)
reads one thing from the
database. But, as you can
see in this code, objects of
the MySqlDataReader
class could get many
things from a database.
Here, I got a moviename
from the movie table, the
firstname from the
customer table, and the id
from the customer table.
Summary
//include the using MySql line at the top
using MySql.Data.MySqlClient;
//create an object of MySqlConnection with the string containing datasource, etc as a parameter
string connectionInfo = "datasource = localhost; port = 3306; username = root; password = pawsox11";
MySqlConnection connect = new MySqlConnection(connectionInfo);
//create an object of MySqlCommand with the SQL Query as the first parameter and the object of MySqlConnection
//as the second parameter
MySqlCommand SQLCommand1 = new MySqlCommand("select * from videostore.customer;”,connect);
try
{
//open the connection using the MySqlConnection object
connect.Open();
//use a DataReader to process each record
MySqlDataReader reader;
reader = SQLCommand1.ExecuteReader();
while (reader.Read()) { //do something with each record }
}
catch (Exception er) {//do something with the exception}
//always close the connection
connect.Close();
References
From the Stanford Online Database Course:
Introduction to SQL:
http://www.youtube.com/watch?feature=player_embedded&v=wxFmiRwXcQY
basic-select-statement:
http://www.youtube.com/watch?feature=player_embedded&v=4IxirOdp6bw
table-variables-set-operators:
http://www.youtube.com/watch?v=-BCCy5Z6i-s&feature=player_embedded
subqueries-in-where:
http://www.youtube.com/watch?v=IJPXosPGLTU&feature=player_embedded
subqueries-in-from-select:
http://www.youtube.com/watch?v=8OCAxk1Rybg&feature=player_embedded
Professor Chi's database class website:
http://163.238.35.144/~chi/CSC715/CSC715.html
Professor Chi's SQL part 1 tutorial:
http://163.238.35.144/~chi/CSC424/SQL/SQL%20Tutorial%20--%20Part%201%20MySQL.htm
C# Visual Studio with MySql Tutorials:
http://www.youtube.com/playlist?list=PLS1QulWo1RIZrmdggzEKbhnfvCMHtT-sA
Professor Gueorguieva's Database with C# lecture:
http://www.cs.csi.cuny.edu/~natacha/TeachSpring_2013/CSC330/CSharp/Lec5/DatabasesCSharp.pdf