I get this error on runtime:
System.InvalidOperationException: ExecuteReader: Connection property has not been initialized.
which is pointing to this line:
SqlDataReader openBuyers = b.ExecuteReader();
I'm using a method from my WCF.
This on svc:
public string ConnectionString()
    {
        string connectToDB = ConfigurationManager.ConnectionStrings["connection"].ToString();
        return connectToDB;
    }
    public SqlConnection OpenConnection()
    {
        try
        {
            SqlConnection linkToDB = new SqlConnection(ConnectionString());
            linkToDB.Open();
            return linkToDB;
        }
        catch (Exception)
        {
            return null;
        }
    }
Added this to my web.config in WCF:
<connectionStrings>
     <add name="connection" connectionString="Data 
     Source=localhost\SQLEXPRESS;Integrated Security=true;Initial
     Catalog=ProductDB"/>
</connectionStrings>