Web Service code not returning array of String

Question

I want to return an array of Strings in the form "abc#xyz#ghi#tru" (where # is delimiter) from my web service method . However i m not able to do it . Here is my current web service code :

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.Xml.Linq;
using System.Data.SqlClient;

namespace WebService10
{
    /// <summary>
    /// Summary description for Service1
    /// </summary>
    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    [ToolboxItem(false)]
    // To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment
 the following line. 
    // [System.Web.Script.Services.ScriptService]
    public class Service1 : System.Web.Services.WebService
    {
        String[] result=new String[40];
        String[] result2 = new String[40];

        [WebMethod]
        public String[] getData()
        {
            SqlConnection myConnection = new SqlConnection(@"Data Source=.\SQLEXPRESS;Initial Catalog=student;User ID=sa;Password=123");
            try
            {
                myConnection.Open();

                SqlCommand myCommand = new SqlCommand();
                myCommand.Connection = myConnection;
                myCommand.CommandText = "select count(*) from names where name =@name";

                SqlDataReader myReader = myCommand.ExecuteReader();

                //while
                for(int i=0;i<40;i++)
                {
                    if (myReader.Read())
                    {
                         result[i]= myReader["name"].ToString();
                         result2[i] = result[i] + "#";
                    }
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            finally
            {
                myConnection.Close();
            }

            return result2;
        }
    }
}

Can anyone tell me what's wrong with my code ?

That's a lot of code. What is it doing? What happens if you change getData() to just return a static value such as "returned string?"{ — Brian Hoover, Jul 30 '11 at 17:39
hey sorry i will explain . I have created a database in SQL Server 2008 having a single column "name" in which i have inserted sample values..I just want to retreive those values in the form i have mentioned in my question along with a delimiter. is there any way to do it ? — Parth Doshi, Jul 30 '11 at 17:42
@kleinohad : yes i have single column "name" with values that I have already inserted . I just need to retreive them now using the method of my web service in the manner i hv mentioned in my post — Parth Doshi, Jul 30 '11 at 17:53
Is there a strong reason for delimiting with a "#" rather than the standard comma? (Because rather than doing string concatenation you can just rely on the web service to serialize your array for you) — Ash Eldritch, Jul 30 '11 at 17:53
@Ash Eldritch : I have no strong reason for using # . I just gave an example. A comma also will do. What exactly do u mean by serialize ? I don't know much abt it ..how can web service serialize my data from database? — Parth Doshi, Jul 30 '11 at 17:56

Emond · Accepted Answer · 2011-07-30T18:08:45.540

Try this:

I changed the query (BTW: the query still doesn't make much sense but I do not know what you really want), the resulting type and the loop.

You forgot to pass the parameter to the query too.

Also: change the exception handling; writing to the console on the server side is not a good idea.

public class Service1 : System.Web.Services.WebService
{

    [WebMethod]
    public String getData(string nameFilter)
    {
        String result = "";

        SqlConnection myConnection = new SqlConnection(@"Data Source=.\SQLEXPRESS;Initial Catalog=student;User ID=sa;Password=123");
        try
        {
            myConnection.Open();

            SqlCommand myCommand = new SqlCommand();
            myCommand.Connection = myConnection;
            myCommand.CommandText = "select name from names where name =@name";
            myCommand.Parameters.AddWithValue("@name", nameFilter);
            SqlDataReader myReader = myCommand.ExecuteReader();

            while(myReader.Read())
            {
                if(result.Length > 0)
                {
                    result += "#";
                }
                result += myReader["name"].ToString();
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }
        finally
        {
            myConnection.Close();
        }

        return result;
    }
}

EDIT

I'd prefer a different approach:

public class Service1 : System.Web.Services.WebService
{

    [WebMethod]
    public String[] getData(string nameFilter)
    {
        var names = new List<string>();
        SqlConnection myConnection = new SqlConnection(@"Data Source=.\SQLEXPRESS;Initial Catalog=student;User ID=sa;Password=123");
        try
        {
            myConnection.Open();

            SqlCommand myCommand = new SqlCommand();
            myCommand.Connection = myConnection;
            myCommand.CommandText = "select name from names where name = @name";
            myCommand.Parameters.AddWithValue("@name", nameFilter);
            SqlDataReader myReader = myCommand.ExecuteReader();

            while(myReader.Read())
            {
                names.Add(myReader["name"].ToString());
            }
        }
        catch (Exception ex)
        {
            //Console.WriteLine(ex.Message);
        }
        finally
        {
            myConnection.Close();
        }

        return names.ToArray();
    }
}

@Emo : thanks a lot for the edits and the code. I tried it..However when I click on invoke button in browser i get this [] ..There is no string array displayed .. — Parth Doshi, Jul 30 '11 at 17:46
@Emo : Yes ur recent edited code runs fine..but i just want a delimiter to be inserted after it fetches each record from my database ...eg: john#ann#joe — Parth Doshi, Jul 30 '11 at 17:51
@Parth_90: I added the delimiter. If you expect a lot of names it might be best to switch back to an array of strings or to a StringBuilder while appending the names. — Emond, Jul 30 '11 at 17:56
Hey thanks !! Actually i dnt have a lot of names to fetch..so will use this only. Thanks for all the help !! :-) — Parth Doshi, Jul 30 '11 at 17:59
@Parth_90: No problem, glad to help. One bit of advise: switch back (if possible) to returning an array of strings. That is much easier and less error prone (what if a name contains a `#`) — Emond, Jul 30 '11 at 18:03
Yes I understood your code. Will surely be useful to me.Thanks a ton for the help and support !! — Parth Doshi, Jul 30 '11 at 18:13

score 2 · Answer 2 · answered Jul 30 '11 at 17:59

 [WebMethod]
    public string getData()//changed to return string
    {

        SqlConnection myConnection = new SqlConnection(@"Data Source=.\SQLEXPRESS;Initial Catalog=student;User ID=sa;Password=123");
        try
        {
            myConnection.Open();

            SqlCommand myCommand = new SqlCommand();
            myCommand.Connection = myConnection;
            myCommand.CommandText = "select name from names";//you can make it select distinct

            SqlDataReader myReader = myCommand.ExecuteReader();
            string toReturn = "";
            while(myReader.Read())
            {
                if (myReader.Read())
                {
                     toReturn += myReader["name"].ToString() + "#";
                }
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }
        finally
        {
            myConnection.Close();
        }

        return toReturn; //# as delimiter
    }

Denis Mitropolskiy · Answer 3 · 2011-07-30T18:14:47.167

1

First, your query returns only number instead of set of rows. So you should use sql like this:

select name from names

Second, to return array you could use List instead of pre-defined arrays: I would be use the following approach:

var result = new List<string>();
while(myReader.Read())
{
  result.Add(reader["name"].ToString() + "#");
}

return result.ToArray();

Or if you want to return a string:

return string.Join("#", result.ToArray())

edited Jul 30 '11 at 18:14

answered Jul 30 '11 at 18:07

Denis Mitropolskiy

71
1
10

Yes I follow your approach and yea it's a better way of doing it than mine. Since I am new to C# especially, I would take some time. But as long as people like u help me understand things better, I feel I will learn things much quickly :-) – Parth Doshi Jul 30 '11 at 18:17

Web Service code not returning array of String

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