Problem reading the connection string value

I am having problem readig the connection string value

Getting the following error:

"Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.InvalidOperationException: The ConnectionString property has not been initialized.
"

       
           ---- WEB.CONFIG CODE ----
  <connectionStrings>
    <add name="DbConnectionString"
     connectionString="Server=server_name;Database=db_name;User ID=user_id;Password=abc123;Trusted_Connection=False;Max Pool Size=100"
     providerName="System.Data.SqlClient" />
  </connectionStrings>
 
--- ASP.NET CODE ---
 
            Dim conn As SqlConnection = New SqlConnection(ConfigurationSettings.AppSettings("DbConnectionString"))
 
sqlComm = New SqlCommand("SELECT * FROM AllOrders WHERE CustomerID = '" & CustomerNo & "'", conn)
 
            conn.Open()
            Dim r As SqlDataReader = sqlComm.ExecuteReader()
            conn.Close()     

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