Set exception number when unable to connect. Fixes #599

Author: bgrainger

src/MySqlConnector/Core/ServerSession.cs

@@ -280,7 +280,7 @@ public async Task ConnectAsync(ConnectionSettings cs, ILoadBalancer loadBalancer
 						lock (m_lock)
 							m_state = State.Failed;
 						Log.Error("Session{0} connecting failed", m_logArguments);
-						throw new MySqlException("Unable to connect to any of the specified MySQL hosts.");
+						throw new MySqlException((int) MySqlErrorCode.UnableToConnectToHost, null, "Unable to connect to any of the specified MySQL hosts.");
 					}
 
 					var byteHandler = m_socket != null ? (IByteHandler) new SocketByteHandler(m_socket) : new StreamByteHandler(m_stream);

src/MySqlConnector/MySql.Data.MySqlClient/MySqlConnection.cs

@@ -242,7 +242,7 @@ private async Task OpenAsync(IOBehavior? ioBehavior, CancellationToken cancellat
 			catch (SocketException ex)
 			{
 				SetState(ConnectionState.Closed);
-				throw new MySqlException("Unable to connect to any of the specified MySQL hosts.", ex);
+				throw new MySqlException((int) MySqlErrorCode.UnableToConnectToHost, null, "Unable to connect to any of the specified MySQL hosts.", ex);
 			}
 
 #if !NETSTANDARD1_3

tests/SideBySide/ConnectAsync.cs

@@ -26,7 +26,15 @@ public async Task ConnectBadHost()
 			using (var connection = new MySqlConnection(csb.ConnectionString))
 			{
 				Assert.Equal(ConnectionState.Closed, connection.State);
-				await Assert.ThrowsAsync<MySqlException>(() => connection.OpenAsync());
+				try
+				{
+					await connection.OpenAsync();
+					Assert.True(false, "Exception not thrown");
+				}
+				catch (MySqlException ex)
+				{
+					Assert.Equal((int) MySqlErrorCode.UnableToConnectToHost, ex.Number);
+				}
 				Assert.Equal(ConnectionState.Closed, connection.State);
 			}
 		}

tests/SideBySide/ConnectSync.cs

@@ -24,7 +24,15 @@ public void ConnectBadHost()
 			using (var connection = new MySqlConnection(csb.ConnectionString))
 			{
 				Assert.Equal(ConnectionState.Closed, connection.State);
-				Assert.Throws<MySqlException>(() => connection.Open());
+				try
+				{
+					connection.Open();
+					Assert.True(false, "Exception not thrown");
+				}
+				catch (MySqlException ex)
+				{
+					Assert.Equal((int) MySqlErrorCode.UnableToConnectToHost, ex.Number);
+				}
 				Assert.Equal(ConnectionState.Closed, connection.State);
 			}
 		}