How to get connection string from app.config in another class library project?

Question

how do I get the connection string from app.config in another "class library project"

in the same class library I can use this code :

 DAL.Properties.Settings.Default.BayrueConnectionString;

but the issue is that I cannot get it from my web app.

thanks enter image description here

Class Libraries use the configuration file of the application that is using them, so the settings need to be in the application's configuration file, not the libraries. Libraries don't use config files. — Tim
– Tim, Commented Jun 25, 2013 at 7:37

Tim Schmelter · Accepted Answer · 2013-06-25 07:41:45Z

4

I think there is no more elegant way than this. Add a static helper method to your class library which returns it.

public sealed class Helper
{
    private Helper()
    {
    }

    public static string GetBayrueConnectionString()
    {
        return DAL.Properties.Settings.Default.BayrueConnectionString;
    }
}

answered Jun 25, 2013 at 7:41

Tim Schmelter

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1 Comment

HAJJAJ Over a year ago

I thinks this one will fix it.

Jakub Konecki · Accepted Answer · 2013-06-25 07:38:42Z

0

Add reference to System.Configuration.

Use System.Configuration.ConfigurationManager.ConnectionStrings["DAL.Properties.Settings.BayrueConnectionString"]

answered Jun 25, 2013 at 7:38

Jakub Konecki

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4 Comments

HAJJAJ Over a year ago

Object reference not set to an instance of an object. this the error I am getting when use your code

Jakub Konecki Over a year ago

Are you sure that the app.config file is located in the folder where you run your app?

HAJJAJ Over a year ago

the app.config is in another project

Jakub Konecki Over a year ago

When you deploy your app all the files need to be in the same folder.

Jeff Odle · Accepted Answer · 2013-06-25 09:28:40Z

First, create a new ConnectionStrings.config file in the project you'd like to reference.

ConnectionStrings.config:

<connectionStrings>
    <add name="DefaultConnection" providerName="System.Data.SqlClient" connectionString="Data                        Source=(LocalDb)\v11.0;Initial Catalog=aspnet-MvcApplication-20130625013234;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\aspnet-MvcApplication-20130625013234.mdf" />
</connectionStrings>

Next, unload your DAL project. Once unloaded, right click > Edit DAL.csproj.

Add the following element to the .csproj with the Include="{the ConnectionStrings.config you'd like to reference}":

<ItemGroup>
    <Content Include="..\ConnectionStrings.config" />
</ItemGroup>

Solution Explorer

Reload your project. This should add a ConnectionStrings.config file, shown above, to your project. Notice that both will open the same file. Now edit the app.config to reference the newly created .config file that was just added to your DAL:

<connectionStrings configSource="ConnectionStrings.config" />

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