Connection events
Applies to: 
.NET Framework
.NET
.NET Standard
The Microsoft SqlClient Data Provider for SQL Server has Connection objects with two events that you can use to retrieve informational messages from a data source or to determine if the state of a Connection has changed. The following table describes the events of the Connection object.
| Event | Description |
|---|---|
| InfoMessage | Occurs when an informational message is returned from a data source. Informational messages are messages from a data source that don't result in an exception being thrown. |
| StateChange | Occurs when the state of the Connection changes. |
Work with the InfoMessage event
You can retrieve warnings and informational messages from a SQL Server data source using the InfoMessage event of the SqlConnection object. Errors returned from the data source with a severity level of 11 through 16 cause an exception to be thrown. However, the InfoMessage event can be used to obtain messages from the data source that aren't associated with an error. With Microsoft SQL Server, any error with a severity of 10 or less is considered to be an informational message, and can be captured by using the InfoMessage event. For more information, see the Database Engine Error Severities article.
The InfoMessage event receives an SqlInfoMessageEventArgs object containing, in its Errors property, a collection of the messages from the data source. You can query the Error objects in this collection for the error number, message text, and the source of the error. The Microsoft SqlClient Data Provider for SQL Server also includes detail about the database, stored procedure, and line number that the message came from.
Example
The following code example shows how to add an event handler for the InfoMessage event.
// Assumes that connection represents a SqlConnection object.
connection.InfoMessage +=
(object sender, SqlInfoMessageEventArgs args) =>
{
foreach (SqlError err in args.Errors)
{
Console.WriteLine(
"The {0} has received a severity {1}, state {2} error number {3}\n" +
"on line {4} of procedure {5} on server {6}:\n{7}",
err.Source, err.Class, err.State, err.Number, err.LineNumber,
err.Procedure, err.Server, err.Message);
}
};
Handle errors as InfoMessages
The InfoMessage event will normally fire only for informational and warning messages that are sent from the server. However, when an actual error occurs, the execution of the ExecuteNonQuery or ExecuteReader method that began the server operation is halted and an exception is thrown.
If you want to continue processing the rest of the statements in a command regardless of any errors produced by the server, set the FireInfoMessageEventOnUserErrors property of the SqlConnection to true. Setting this property causes the connection to fire the InfoMessage event for errors instead of throwing an exception and interrupting processing. The client application can then handle this event and respond to error conditions.
Note
An error with a severity level of 17 or above that causes the server to stop processing the command must be handled as an exception. In this case, an exception is thrown regardless of how the error is handled in the InfoMessage event.
Work with the StateChange event
The StateChange event occurs when the state of a Connection changes. The StateChange event receives StateChangeEventArgs that enable you to determine the change in state of the Connection by using the OriginalState and CurrentState properties. The OriginalState property is a ConnectionState enumeration that indicates the state of the Connection before it changed. CurrentState is a ConnectionState enumeration that indicates the state of the Connection after it changed.
The following code example uses the StateChange event to write a message to the console when the state of the Connection changes.
// Assumes that connection represents a SqlConnection object.
connection.StateChange +=
(object sender, StateChangeEventArgs args) =>
{
Console.WriteLine(
"The current Connection state has changed from {0} to {1}.",
args.OriginalState, args.CurrentState);
};