Backend sent unrecognized response type: u Error with Postgres 9.3 and npgsql - postgresql

Question

I upgraded my server yesterday from Postgres 9.1 to 9.3 and since then I've been getting an error: Backend sent unrecognized response type: u
I'm using npgsql to connect from my application to the server.
I remember that I used to get this error a while back and I haven't seen it in a while.
A full line from my log is:
Backend sent unrecognized response type: u
INSERT INTO stockcodes_rating (item_code,rating,price_range,user_id,timestamp_of_rating) VALUES ('10245684','5','Reasonable','10832',now())
My code for the procedure is:
Public Function InsertRating(ByVal Stockcode As String, ByVal Rating As Integer, ByVal PriceRange As String, ByVal UserId As String) As String
Dim objDBWrite As dlNpgSQL
objDBWrite = New dlNpgSQL("PostgreConnectionStringWrite", ConfigurationManager.AppSettings("CurrentDatabase"))
tmpSQL = "INSERT INTO stockcodes_rating (item_code,rating,price_range,user_id,timestamp_of_rating) VALUES " & _
"('" & Stockcode.ToUpper & "','" & Rating & "','" & PriceRange & "','" & UserId & "',now())"
Try
objDBWrite.ExecuteQuery(tmpSQL)
Catch ex As Exception
objDBWrite.CloseConnection()
Return ex.Message
Finally
objDBWrite.CloseConnection()
End Try
Return "Success"
End Function
My code for the dlNpgSQLclass is:
Imports Npgsql
Public Class dlNpgSQL
Dim _sqlConnection As NpgsqlConnection
Dim _sqlCommand As NpgsqlCommand
Dim _sqlDataAdapter As NpgsqlDataAdapter
Dim _dataset As DataSet
Public Sub New()
On Error GoTo ErrZ
_sqlConnection = New NpgsqlConnection(ConfigurationManager.ConnectionStrings("PostgreRemoteConnectionString").ConnectionString)
Exit Sub
End Sub
Public Sub New(ByVal WhichConnectionString As String)
On Error GoTo ErrZ
_sqlConnection = New NpgsqlConnection(ConfigurationManager.ConnectionStrings(WhichConnectionString).ConnectionString)
Exit Sub
End Sub
Public Sub New(ByVal WhichConnectionString As String, ByVal WhichDB As String)
On Error GoTo ErrZ
_sqlConnection = New NpgsqlConnection(ConfigurationManager.ConnectionStrings(WhichConnectionString).ConnectionString & "database=" & WhichDB & ";")
Exit Sub
End Sub
Public Function OpenConnection() As NpgsqlConnection
Try
If _sqlConnection.State = ConnectionState.Closed Then
_sqlConnection.Open()
End If
Catch ex As Exception
End Try
Return _sqlConnection
End Function
Public Sub CloseConnection()
Try
If _sqlConnection.State = ConnectionState.Open Then
_sqlConnection.Close()
End If
Catch ex As Exception
End Try
End Sub
Public Function GetDataSet(ByVal strQuery As String) As DataSet
'NpgsqlEventLog.Level = LogLevel.Normal
'NpgsqlEventLog.LogName = ("c:\npgsql.log")
'NpgsqlEventLog.EchoMessages = True
_dataset = New DataSet
Try
_sqlDataAdapter = New NpgsqlDataAdapter(strQuery, OpenConnection)
_sqlDataAdapter.Fill(_dataset)
Catch ex As Exception
End Try
Return _dataset
End Function
Public Function ReleaseDataSet(ByRef ds As DataSet) As Boolean
Try
ds.Clear()
ds.Dispose()
Catch ex As Exception
End Try
Return True
End Function
Public Function ExecuteQuery(ByVal strQuery As String) As String
'NpgsqlEventLog.Level = LogLevel.Normal
'NpgsqlEventLog.LogName = ("c:\npgsql.log")
'NpgsqlEventLog.EchoMessages = True
Dim RecordsReturned As String = ""
Try
_sqlCommand = New NpgsqlCommand(strQuery, OpenConnection)
RecordsReturned = _sqlCommand.ExecuteNonQuery()
Catch ex As Exception
Return ""
End Try
Return RecordsReturned
End Function
Public Function isR(ByVal tmpDs As DataSet, Optional ByVal tablename As Integer = 0) As Boolean
Try
If tmpDs.Tables.Count > 0 Then
If tmpDs.Tables(0).Rows.Count > 0 Then
isR = True
Else
isR = False
End If
End If
Catch ex As Exception
isR = False
End Try
End Function
End Class

Answer 1

What version of npgsql are you using? You probably need to upgrade to 2.0.14.3.
Better yet, try out the 2.1.0-beta1 which is quite stable and about to be released.

Answer 2

The same thing happened to me using Npgsql 2.0.12.0 sharing the connection between threads. Making a new connection in each thread was the solution!