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• Opening a Connection to a Single Server

• Opening a Connection for Multiple Hosts with Failover

• Opening a Connection Using a Single DNS Domain

After 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 aMySqlConnection object, assign the connection string, and open the connection.

MySQL Connector/NET can also connect using the native Windows authentication plugin. SeeSection 4.4, “Connector/NET Authentication” for details.

You can further extend the authentication mechanism by writing your own authentication plugin. SeeSection 5.8, “Writing a Custom Authentication Plugin” for details.

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);}

Visual Basic Example

Dim conn As New MySql.Data.MySqlClient.MySqlConnectionDim myConnectionString as StringmyConnectionString = "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

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

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);}

Visual Basic Example

Dim myConnectionString as StringmyConnectionString = "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

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

Data used by applications can be stored on multiple MySQL servers to provide high availability. Connector/NET provides a simple way to specify multiple hosts in a connection string for cases in which multiple MySQL servers are configured for replication and you are not concerned about the precise server your application connects to in the set. For an example of how to configure multiple hosts with replication, see Using Replication & Load balancing.

Starting in Connector/NET 8.0.19, both classic MySQL protocol and X Protocol connections permit the use of multiple host names and multiple endpoints (ahost:port pair) in a connection string or URI scheme. For example:

// classic protocol example"server=10.10.10.10:3306,192.101.10.2:3305,localhost:3306;uid=test;password=xxxx"// X Protocol examplemysqlx://test:test@[192.1.10.10:3305,127.0.0.1:3306]

An updated failover approach selects the target for connection first by priority order, if provided, or random order when no priority is specified. If the attempted connection to a selected target is unsuccessful, Connector/NET selects a new target from the list until no more hosts are available. If enabled, Connector/NET uses connection pooling to manage unsuccessful connections (seeSection 4.2, “Managing a Connection Pool in Connector/NET”).

When multiple MySQL instances provide the same service in your installation, you can apply DNS Service (SRV) records to provide failover, load balancing, and replication services. DNS SRV records remove the need for clients to identify each possible host in the connection string, or for connections to be handled by an additional software component. They can also be updated centrally by administrators when servers are added or removed from the configuration or when their host names are changed. DNS SRV records can be used in combination with connection pooling, in which case connections to hosts that are no longer in the current list of SRV records are removed from the pool when they become idle. For information about DNS SRV support in MySQL, seeConnecting to the Server Using DNS SRV Records.

A service record is a specification of data managed by your domain name system that defines the location (host name and port number) of servers for the specified services. The record format defines the priority, weight, port, and target for the service as defined in the RFC 2782 specification (seehttps://tools.ietf.org/html/rfc2782). In the following SRV record example with four server targets (for_mysql._tcp.foo.abc.com.), Connector/NET uses the server selection order offoo2,foo1,foo3, andfoo4.

Name                      TTL   Class   Priority Weight Port  Target_mysql._tcp.foo.abc.com. 86400 IN SRV   0        5      3306  foo1.abc.com_mysql._tcp.foo.abc.com. 86400 IN SRV   0        10     3306  foo2.abc.com_mysql._tcp.foo.abc.com. 86400 IN SRV   10       5      3306  foo3.abc.com_mysql._tcp.foo.abc.com. 86400 IN SRV   20       5      3306  foo4.abc.com

To open a connection using DNS SRV records, add thedns-srv connection option to your connection string. For example:

C# Example

var conn = new MySqlConnection("server=_mysql._tcp.foo.abc.com.;dns-srv=true;" +             "user id=user;password=****;database=test");

For additional usage examples and restrictions for both classic MySQL protocol and X Protocol, seeOptions for Both Classic MySQL Protocol and X Protocol.