ClientDisconnectedConnectionAdapter.cs

/// <summary>
/// Creates a connection adapter that cancels any <see cref="IDbCommand"/> created from it when the client disconnects from the response.
/// </summary>
private class ClientDisconnectedConnectionAdapter : IDbConnection
{
    private readonly SqlConnection _connection;
    
    public conn(SqlConnection sqlConnection)
    {
        _connection = sqlConnection ?? throw new ArgumentNullException(nameof(sqlConnection));
    }

    public string ConnectionString { get => _connection.ConnectionString; set => _connection.ConnectionString = value; }

    public int ConnectionTimeout => _connection.ConnectionTimeout;

    public string Database => _connection.Database;

    public ConnectionState State => _connection.State;

    public IDbTransaction BeginTransaction()
    {
        return _connection.BeginTransaction();
    }

    public IDbTransaction BeginTransaction(IsolationLevel il)
    {
        return _connection.BeginTransaction(il);
    }

    public void ChangeDatabase(string databaseName)
    {
        _connection.ChangeDatabase(databaseName);
    }

    public void Close()
    {
        _connection.Close();
    }

    public IDbCommand CreateCommand()
    {
        IDbCommand command = _connection.CreateCommand();

        try
        {
            // context may not be available - there's not a robust way of checking before getting the 'context is unavailable exception'
            HttpContext.Current.Response.ClientDisconnectedToken.Register(() =>
            {
                try
                {
                    // don't break the request if the cancel fails
                    command.Cancel();
                }
                catch(Exception e)
                {
                    System.Diagnostics.Trace.TraceError($"Failed to canel db command from http response register ClientDisconnectedToken callback. {e.Message}");
                }
            });
        }
        catch(Exception e)
        {
            System.Diagnostics.Trace.TraceError($"Failed to register callback for db command. {e.Message}");
        }

        return command;
    }

    public void Dispose()
    {
        _connection.Dispose();
    }

    public void Open()
    {
        _connection.Open();
    }
}