How to write connection string in web.config file and read from it?

Question

I'm trying to write Connection string to Web.config like this:

<connectionStrings>
  <add name="Dbconnection" connectionString="Server=localhost; 
       Database=OnlineShopping ; Integrated Security=True"/>
</connectionStrings >

and read from it like this:

string strcon = 
    ConfigurationManager.ConnectionStrings["Dbconnection"].ConnectionString;
SqlConnection DbConnection = new SqlConnection(strcon);

when run the program I get an error because of the null reference. but when I use this code:

SqlConnection DbConnection = new SqlConnection();
DbConnection.ConnectionString = 
    "Server=localhost; Database=OnlineShopping ; Integrated Security=True";

I don't get any error and the program works correctly! What is the problem?

Answer 1

Add reference to add System.Configuration:-

System.Configuration.ConfigurationManager.
    ConnectionStrings["connectionStringName"].ConnectionString;

Also you can change the WebConfig file to include the provider name:-

<connectionStrings>
  <add name="Dbconnection" 
       connectionString="Server=localhost; Database=OnlineShopping;
       Integrated Security=True"; providerName="System.Data.SqlClient" />
</connectionStrings>