Error with App.config connectionstrign in class library

Question

I have an error with connection string in class library project. In Appconfig I have this code:

  <connectionStrings>
    <add name="DefaultConnection" connectionString="Data Source=DESKTOP-123\SQLEXPRESS;Initial Catalog=MyDb;User ID=sa;Password=mypassword"  providerName="System.Data.SqlClient"/>
  </connectionStrings>

Connection string I call form a static function:

public static string ConnDb {
        get {
            return ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;
        }
    }

When I use this connection string in function

Sqlconnection conn = new Sqlconnection(Class1.ConnDb)

I have some error like

{"Object reference not set to an instance of an object."}

What can I do?

Where is the error occurring in the code? Have you stepped through the code to see what object is giving you the null reference? — Barry O'Kane, Jun 02 '17 at 10:14
Libraries don't have app.config, the running process does so put that connection string in the config of the running project. — Crowcoder, Jun 02 '17 at 10:18
Possible duplicate of [app.config for a class library](https://stackoverflow.com/questions/5674971/app-config-for-a-class-library) — Federico Dipuma, Jun 02 '17 at 10:27
App.config need to be in the project which uses this class library. Try that and let us know if you still face the issue — Chetan, Jun 02 '17 at 11:41

score 1 · Answer 1 · answered Jun 02 '17 at 11:00

1

you can user appSettings for alternative option.

answered Jun 02 '17 at 11:00

ishan joshi

270
3
13

Won't work if file is not part of calling application. – Chetan Jun 02 '17 at 11:41
And connection strings are not usually per-user settings – Crowcoder Jun 02 '17 at 12:18

Error with App.config connectionstrign in class library

1 Answers1