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20.2.4.4 Using Connector/NET with Connection Pooling »
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20.2.4.3. Creating a Connection String

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20.2.4.3.1. Opening a Connection
20.2.4.3.2. Handling Connection Errors

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 user name of root and a password of 12345. The default database for all statements will be the test database.

The following options are available:

Note

Using the '@' symbol for parameters is now the preferred approach although the old pattern of using '?' is still supported.

Please be aware however that using '@' can cause conflicts when user variables are also used. To help with this situation please see the documentation on the Allow User Variables connection string option, which can be found here: Section 20.2.4.3, “Creating a Connection String”. The Old Syntax connection string option has now been deprecated.

20.2.4.3.1. 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.

20.2.4.3.2. 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 user name 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;");