VB.NET Connection string (Web.Config, App.Config)

Question

Really having an annoying time with connection strings.

I have two projects together in a single solution. A Web forms application acting as the presentation layer, and a class library supporting it which will send and receive data from a database.  

-- The Employee Class within the Class Library Project --

Friend Class Employee

Public Function GetEmployees() As DataSet

    Dim DBConnection As New SqlConnection(My_ConnectionString)
    Dim MyAdapter As New SqlDataAdapter("exec getEmployees", DBConnection)

    Dim EmployeeInfo As DataSet
    MyAdapter.Fill(EmployeeInfo, "EmployeeInfo")

    Return EmployeeInfo

End Function

End Class

Currently the application is telling me it cannot access "My_ConnectionString" which I have attempted to store within a config file for quick repeated access:

<configuration>

<system.web>
  <compilation debug="true" strict="false" explicit="true" targetFramework="4.5" />
  <httpRuntime targetFramework="4.5"  />
</system.web>

 <connectionStrings>
   <add name="My_ConnectionString" connectionString="Data Source=.\sqlexpress;Initial Catalog=My_DB;Integrated Security=True;"/>
 </connectionStrings>

</configuration>

The web.config is part of the web form project and not the class library, are these projects unable to 'talk' to each other? Do I need to add a web / app config file to the class library to store a connection string within that project?

Solution 1

Not clear where My_ConnectionString is coming from in your example, but try this

System.Configuration.ConfigurationManager.ConnectionStrings("My_ConnectionString").ConnectionString

like this

Dim DBConnection As New SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings("My_ConnectionString").ConnectionString)

Solution 2

If it's a .mdf database and the connection string was saved when it was created, you should be able to access it via:

    Dim cn As SqlConnection = New SqlConnection(My.Settings.DatabaseNameConnectionString)

Hope that helps someone.

Solution 3

Connection in APPConfig

<connectionStrings>
  <add name="ConnectionString" connectionString="Data Source=192.168.1.25;Initial Catalog=Login;Persist Security Info=True;User ID=sa;Password=example.com"   providerName="System.Data.SqlClient" />
</connectionStrings>

In Class.Cs

public string ConnectionString
{
    get
    {
        return System.Configuration.ConfigurationManager.ConnectionStrings["ConnectionString"].ToString();
    }
}

Comments

[Tim]

You can also add a reference to System.Configuration, import it with Imports System.Configuration and then access it with the shorter ConfigurationManager.ConnectionStrings("My_ConnectionString"‌​).ConnectionString.

[Tim]

I would also suggest using a Using block to ensure the connection is properly disposed of.

[Corgalas]

'ConfigurationManager' is not a member of 'Configuration' I feel like I've made a mistake somewhere...

[Tim]

@Corgalas - Did you add a reference to System.Configuration in your project (the DLL) and add an Imports System.Configuration statement?

[Corgalas]

Forgot the add the reference to the project. Thanks Tim!

[cramopy]

Would you please add some explanation to your code? Thanks!

[Phil3992]

This connection string has hard coded entries,it's not getting them from the .config. What if you need to point to a different server? With this code the application would need deploying with the changes. With .config it can be changed in the background

[SRoy]

this answer solved my problem and I think this is the best practice to declare connection sting by it's name. it helps migration process

[Brandon Barkley]

I have never understood why System.Configuration isn't included by default.