Connecting to MySQL Using Connector/NET


25.2.5.1.1. Introduction

All interaction between a .NET application and the MySQL server is routed through a MySqlConnection object. Before your application can interact with the server, a MySqlConnection object must be instanced, configured, and opened.

Even when using the MySqlHelper class, a MySqlConnection object is created by the helper class.

In this section, we will describe how to connect to MySQL using the MySqlConnection object.

25.2.5.1.2. Creating a Connection String

The MySqlConnection object is configured using a connection string. A connection string contains sever key/value pairs, separated by semicolons. Each key/value pair is joined with an equals sign.

The following is a sample connection string:

    Server=127.0.0.1;Uid=root;Pwd=12345;Database=test;

In this example, the MySqlConnection object is configured to connect to a MySQL server at 127.0.0.1, with a username of root and a password of 12345. The default database for all statements will be the test database.

The following options are typically used (a full list of options is available in the API documentation for Sección 25.2.3.3.15, “ConnectionString”):

  • Server: The name or network address of the instance of MySQL to which to connect. The default is localhost. Aliases include host, Data Source, DataSource, Address, Addr and Network Address.
  • Uid: The MySQL user account to use when connecting. Aliases include User Id, Username and User name.
  • Pwd: The password for the MySQL account being used. Alias Password can also be used.
  • Database: The default database that all statements are applied to. Default is mysql. Alias Initial Catalog can also be used.
  • Port: The port MySQL is using to listen for connections. Default is 3306. Specify -1 for this value to use a named-pipe connection.
25.2.5.1.3. Opening a Connection

Once you have created a connection string it can be used to open a connection to the MySQL server.

The following code is used to create a MySqlConnection object, assign the connection string, and open the connection.

Visual Basic Example

Dim conn As New MySql.Data.MySqlClient.MySqlConnection
Dim myConnectionString as String

myConnectionString = "server=127.0.0.1;" _
            & "uid=root;" _
            & "pwd=12345;" _
            & "database=test;"

Try
  conn.ConnectionString = myConnectionString
  conn.Open()

Catch ex As MySql.Data.MySqlClient.MySqlException
  MessageBox.Show(ex.Message)
End Try

C# Example

MySql.Data.MySqlClient.MySqlConnection conn;
string myConnectionString;
    
myConnectionString = "server=127.0.0.1;uid=root;" +
    "pwd=12345;database=test;";
  
try
{
    conn = new MySql.Data.MySqlClient.MySqlConnection();
    conn.ConnectionString = myConnectionString;
    conn.Open();
}
catch (MySql.Data.MySqlClient.MySqlException ex)
{
    MessageBox.Show(ex.Message);
}

You can also pass the connection string to the constructor of the MySqlConnection class:

Visual Basic Example

Dim myConnectionString as String

myConnectionString = "server=127.0.0.1;" _
              & "uid=root;" _
              & "pwd=12345;" _
              & "database=test;" 

Try
    Dim conn As New MySql.Data.MySqlClient.MySqlConnection(myConnectionString)
    conn.Open()
Catch ex As MySql.Data.MySqlClient.MySqlException
   MessageBox.Show(ex.Message)
End Try

C# Example

MySql.Data.MySqlClient.MySqlConnection conn;
string myConnectionString;

myConnectionString = "server=127.0.0.1;uid=root;" +
    "pwd=12345;database=test;";

try
{
    conn = new MySql.Data.MySqlClient.MySqlConnection(myConnectionString);
    conn.Open();
}
catch (MySql.Data.MySqlClient.MySqlException ex)
{
    MessageBox.Show(ex.Message);
}

Once the connection is open it can be used by the other Connector/NET classes to communicate with the MySQL server.

25.2.5.1.4. Handling Connection Errors

Because connecting to an external server is unpredictable, it is important to add error handling to your .NET application. When there is an error connecting, the MySqlConnection class will return a MySqlException object. This object has two properties that are of interest when handling errors:

  • Message: A message that describes the current exception.
  • Number: The MySQL error number.

When handling errors, you can your application’s response based on the error number. The two most common error numbers when connecting are as follows:

  • 0: Cannot connect to server.
  • 1045: Invalid username and/or password.

The following code shows how to adapt the application’s response based on the actual error:

Visual Basic Example

Dim myConnectionString as String

myConnectionString = "server=127.0.0.1;" _
          & "uid=root;" _
          & "pwd=12345;" _
          & "database=test;" 

Try
    Dim conn As New MySql.Data.MySqlClient.MySqlConnection(myConnectionString)
    conn.Open()
Catch ex As MySql.Data.MySqlClient.MySqlException
    Select Case ex.Number
        Case 0
            MessageBox.Show("Cannot connect to server. Contact administrator")
        Case 1045
            MessageBox.Show("Invalid username/password, please try again")
    End Select
End Try

C# Example

MySql.Data.MySqlClient.MySqlConnection conn;
string myConnectionString;

myConnectionString = "server=127.0.0.1;uid=root;" +  
    "pwd=12345;database=test;";

try
{
    conn = new MySql.Data.MySqlClient.MySqlConnection(myConnectionString);
    conn.Open();
}
    catch (MySql.Data.MySqlClient.MySqlException ex)
{
    switch (ex.Number)
    {
        case 0:
            MessageBox.Show("Cannot connect to server.  Contact administrator");
        case 1045:
            MessageBox.Show("Invalid username/password, please try again");
    }
}

Important: Note that if you are using multilanguage databases you must specify the character set in the connection string. If you do not specify the character set, the connection defaults to the latin1 charset. You can specify the character set as part of the connection string, for example:

MySqlConnection myConnection = new MySqlConnection("server=127.0.0.1;uid=root;" +
    "pwd=12345;database=test;Charset=latin1;");
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