/// <summary>
/// Cancel a connection that is in the process of opening.
/// </summary>
public bool CancelConnect(CancelConnectParams cancelParams)
{
// Validate parameters
if (cancelParams == null || string.IsNullOrEmpty(cancelParams.OwnerUri))
{
return(false);
}
CancelTokenKey cancelKey = new CancelTokenKey
{
OwnerUri = cancelParams.OwnerUri,
Type = cancelParams.Type
};
// Cancel any current connection attempts for this URI
CancellationTokenSource source;
if (cancelTupleToCancellationTokenSourceMap.TryGetValue(cancelKey, out source))
{
try
{
source.Cancel();
return(true);
}
catch
{
return(false);
}
}
return(false);
}
/// <summary>
/// Tries to create and open a connection with the given ConnectParams.
/// </summary>
/// <returns>null upon success, a ConnectionCompleteParams detailing the error upon failure</returns>
private async Task <ConnectionCompleteParams> TryOpenConnection(ConnectionInfo connectionInfo, ConnectParams connectionParams)
{
CancellationTokenSource source = null;
DbConnection connection = null;
CancelTokenKey cancelKey = new CancelTokenKey {
OwnerUri = connectionParams.OwnerUri, Type = connectionParams.Type
};
ConnectionCompleteParams response = new ConnectionCompleteParams {
OwnerUri = connectionInfo.OwnerUri, Type = connectionParams.Type
};
try
{
// build the connection string from the input parameters
string connectionString = BuildConnectionString(connectionInfo.ConnectionDetails);
// create a sql connection instance
connection = connectionInfo.Factory.CreateSqlConnection(connectionString);
connectionInfo.AddConnection(connectionParams.Type, connection);
// Add a cancellation token source so that the connection OpenAsync() can be cancelled
using (source = new CancellationTokenSource())
{
// Locking here to perform two operations as one atomic operation
lock (cancellationTokenSourceLock)
{
// If the URI is currently connecting from a different request, cancel it before we try to connect
CancellationTokenSource currentSource;
if (cancelTupleToCancellationTokenSourceMap.TryGetValue(cancelKey, out currentSource))
{
currentSource.Cancel();
}
cancelTupleToCancellationTokenSourceMap[cancelKey] = source;
}
// Create a task to handle cancellation requests
var cancellationTask = Task.Run(() =>
{
source.Token.WaitHandle.WaitOne();
try
{
source.Token.ThrowIfCancellationRequested();
}
catch (ObjectDisposedException)
{
// If ObjectDisposedException was thrown, then execution has already exited the
// "using" statment and source was disposed, meaning that the openTask completed
// successfully. This results in a ObjectDisposedException when trying to access
// source.Token and should be ignored.
}
});
var openTask = Task.Run(async() =>
{
await connection.OpenAsync(source.Token);
});
// Open the connection
await Task.WhenAny(openTask, cancellationTask).Unwrap();
source.Cancel();
}
}
catch (SqlException ex)
{
response.ErrorNumber = ex.Number;
response.ErrorMessage = ex.Message;
response.Messages = ex.ToString();
return(response);
}
catch (OperationCanceledException)
{
// OpenAsync was cancelled
response.Messages = SR.ConnectionServiceConnectionCanceled;
return(response);
}
catch (Exception ex)
{
response.ErrorMessage = ex.Message;
response.Messages = ex.ToString();
return(response);
}
finally
{
// Remove our cancellation token from the map since we're no longer connecting
// Using a lock here to perform two operations as one atomic operation
lock (cancellationTokenSourceLock)
{
// Only remove the token from the map if it is the same one created by this request
CancellationTokenSource sourceValue;
if (cancelTupleToCancellationTokenSourceMap.TryGetValue(cancelKey, out sourceValue) && sourceValue == source)
{
cancelTupleToCancellationTokenSourceMap.TryRemove(cancelKey, out sourceValue);
}
}
}
// Return null upon success
return(null);
}
/// <summary>
/// Tries to create and open a connection with the given ConnectParams.
/// </summary>
/// <returns>null upon success, a ConnectionCompleteParams detailing the error upon failure</returns>
private async Task <ConnectionCompleteParams> TryOpenConnection(ConnectionInfo connectionInfo, ConnectParams connectionParams)
{
CancellationTokenSource source = null;
DbConnection connection = null;
CancelTokenKey cancelKey = new CancelTokenKey {
OwnerUri = connectionParams.OwnerUri, Type = connectionParams.Type
};
ConnectionCompleteParams response = new ConnectionCompleteParams {
OwnerUri = connectionInfo.OwnerUri, Type = connectionParams.Type
};
try
{
// build the connection string from the input parameters
string connectionString = BuildConnectionString(connectionInfo.ConnectionDetails);
// create a sql connection instance
connection = connectionInfo.Factory.CreateSqlConnection(connectionString);
connectionInfo.AddConnection(connectionParams.Type, connection);
// Add a cancellation token source so that the connection OpenAsync() can be cancelled
source = new CancellationTokenSource();
// Locking here to perform two operations as one atomic operation
lock (cancellationTokenSourceLock)
{
// If the URI is currently connecting from a different request, cancel it before we try to connect
CancellationTokenSource currentSource;
if (cancelTupleToCancellationTokenSourceMap.TryGetValue(cancelKey, out currentSource))
{
currentSource.Cancel();
}
cancelTupleToCancellationTokenSourceMap[cancelKey] = source;
}
// Open the connection
await connection.OpenAsync(source.Token);
}
catch (SqlException ex)
{
response.ErrorNumber = ex.Number;
response.ErrorMessage = ex.Message;
response.Messages = ex.ToString();
return(response);
}
catch (OperationCanceledException)
{
// OpenAsync was cancelled
response.Messages = SR.ConnectionServiceConnectionCanceled;
return(response);
}
catch (Exception ex)
{
response.ErrorMessage = ex.Message;
response.Messages = ex.ToString();
return(response);
}
finally
{
// Remove our cancellation token from the map since we're no longer connecting
// Using a lock here to perform two operations as one atomic operation
lock (cancellationTokenSourceLock)
{
// Only remove the token from the map if it is the same one created by this request
CancellationTokenSource sourceValue;
if (cancelTupleToCancellationTokenSourceMap.TryGetValue(cancelKey, out sourceValue) && sourceValue == source)
{
cancelTupleToCancellationTokenSourceMap.TryRemove(cancelKey, out sourceValue);
}
source?.Dispose();
}
}
// Return null upon success
return(null);
}
