Unable to Get the data from database

Hi, I am new to webservices, I create a webservice which give access to a database which stores some book details.

I created a webservice to get the book details, here is the code for that.

[WebMethod]
public DataSet getBookDetails()
        {
            DBConnection connect = new DBConnection();
            DataSet dataset = null;
            try
            {
               dataset = connect.connectToDB();
            }
            catch (Exception ex)
            {
                ex.Message.ToString();
            }
            return dataset;
        }

Where DBconnection class , connect to the database and connectTpDB method returns the book details in dataset. it is working fine in console application,

When I call this methos in this webmethod, it gives following wsdl file,

Thanks