Can't get the connection string from app.config

Question

I have a class library that contains classes shared by an asp.net web application and a WCF web service. The classes inside the library need to retrieve information from the database, and so the library has an entry in the app.config for the connection string, and a method that retrieves that connection string.

Here's how I declare my connection string in the app.config :

<configuration>
    <connectionStrings>
        <add name="connstring"
             connectionString="Data Source=MYSERVER;Initial Catalog=MY_DB;User Id=mylogin;Password=mypassword;"
             providerName="System.Data.SqlClient"/>
    </connectionStrings>
    [...]
</configuration>

And here's the method that retrieves the connection string :

Imports System.Configuration
Imports System.Data.SqlClient
Imports System.Data.OleDb

Public Module modGen

    Public Function gGetConnectionString() As String

        Dim conn As ConnectionStringSettings = ConfigurationManager.ConnectionStrings("connstring")
        Dim connString As String = conn.ConnectionString
        Return connString

    End Function

The problem is that, when the method runs, "conn" gets "Nothing" for value and the following exception is then thrown :

System.TypeInitializationException was caught
  Message=The type initializer for 'CHK.TRK.CLS.modGen' threw an exception.
  Source=CHK.TRK.CLS
  TypeName=CHK.TRK.CLS.modGen
  StackTrace:
       at CHK.TRK.CLS.modGen.gGetConnectionString()
       at CHK.TRK.CLS.modAuth.CheckUser(String logon, String pwHash) in  H:\WorkSpace\CHKTRK\CHKTRK\CHKTRKClasses\Mod\modAuth.vb:line 141
       at CHK.TRK.CLS.modAuth.Authenticate(String logon, String pwhash) in H:\WorkSpace\CHKTRK\CHKTRK\CHKTRKClasses\Mod\modAuth.vb:line 9
       at CHKTRKWebService.CheckTrackService.Authenticate(String login, String pwHash) in H:\WorkSpace\CHKTRK\CHKTRK\CHKTRKWebService\CheckTrackService.svc.vb:line 20
  InnerException: System.NullReferenceException
       Message=Object reference not set to an instance of an object.
       Source=CHK.TRK.CLS
       StackTrace:
            at CHK.TRK.CLS.modGen..cctor() in H:\WorkSpace\CHKTRK\CHKTRK\CHKTRKClasses\Mod\modGen.vb:line 138
       InnerException:

Is there something wrong with the way I declare my connection string in the app.config file, or with the method that retrieves it ?

score 1 · Accepted Answer · edited May 23 '17 at 12:05

1

Add the connection string to the web.config of your asp.net application.

You may check the solution given here

edited May 23 '17 at 12:05

Community

1
1

answered Oct 29 '13 at 09:55

Giannis Paraskevopoulos

18,261
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It's already in the web.config of both the asp.net app and the WCF service. And it has the same name is the three config files. – ZipionLive Oct 29 '13 at 10:01
You have mentioned that this connection string is in the library's app.config. Are you sure it exists in the web.config too? – Giannis Paraskevopoulos Oct 29 '13 at 10:03
1

Yes, it is declared in the exact same way in the web app's web.config. – ZipionLive Oct 29 '13 at 10:04
It worked after closing and re-opening the project in VS. Thanks for your help! – ZipionLive Oct 29 '13 at 10:51

score 1 · Answer 2 · answered Oct 29 '13 at 10:00

Add the connection string like this :ConfigurationManager.ConnectionStrings Property

Sample Code:

Public Shared Sub ReadConnectionStrings()

    ' Get the ConnectionStrings collection. 
    Dim connections _
        As ConnectionStringSettingsCollection = _
            ConfigurationManager.ConnectionStrings

    If connections.Count <> 0 Then
        Console.WriteLine()
        Console.WriteLine( _
            "Using ConnectionStrings property.")
        Console.WriteLine( _
            "Connection strings:")

        ' Get the collection elements. 
        For Each connection _
            As ConnectionStringSettings In connections
            Dim name As String = connection.Name
            Dim provider As String = _
                connection.ProviderName
            Dim connectionString As String = _
                connection.ConnectionString

            Console.WriteLine( _
                "Name:               {0}", name)
            Console.WriteLine( _
                "Connection string:  {0}", _
                    connectionString)
            Console.WriteLine( _
                "Provider:            {0}", provider)
        Next 
    Else
        Console.WriteLine()
        Console.WriteLine( _
            "No connection string is defined.")
        Console.WriteLine()
    End If 
End Sub

This wasn't the actual answer but it helped me a lot anyway, thanks ! — ZipionLive, Oct 29 '13 at 10:49
ya this is not real and but this is sample code for to get idea abot how to get connection string — Jignesh.Raj, Oct 29 '13 at 10:59

Can't get the connection string from app.config

2 Answers2

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