SqlConnection.OpenAsync Method (CancellationToken)
An asynchronous version of Open, which opens a database connection with the property settings specified by the ConnectionString. The cancellation token can be used to request that the operation be abandoned before the connection timeout elapses. Exceptions will be propagated via the returned Task. If the connection timeout time elapses without successfully connecting, the returned Task will be marked as faulted with an Exception. The implementation returns a Task without blocking the calling thread for both pooled and non-pooled connections.
Assembly: System.Data (in System.Data.dll)
Calling OpenAsync more than once for the same instance before task completion.
Context Connection=true is specified in the connection string.
A connection was not available from the connection pool before the connection time out elapsed.
Any error returned by SQL Server that occurred while opening the connection.
After calling OpenAsync, State must return Connecting until the returned Task is completed. Then, if the connection was successful, State must return Open. If the connection fails, State must return Closed.
For more information about asynchronous programming in the .NET Framework Data Provider for SQL Server, see Asynchronous Programming.