Populate listbox from WCF

Question

I am struggling greatly on how to populate listbox from the WCF. This is my old code i used before I have tried to implement my WCF:

lstProcesses.BeginUpdate();
        lstProcesses.Items.Clear();
        while (dr.Read())
        {
            lstProcesses.Items.Add(dr.GetString(0));
        }
        dr.Close();
        con.Close();
        lstProcesses.EndUpdate();*/

My New attempted code was:

public void ShowData2()
    {

        try
        {

            ServiceReference6.Service1Client obj6 = new ServiceReference6.Service1Client();
            if (obj6.SelectSavedProcessInformation())
            {

                string passed = "";

            lstProcesses.Items.Add(obj6);

            }
            else
            {

                string failed = "";

            }
        }
        catch
        {


        }
    }

My WCF consists of this:

 public bool SelectSavedProcessInformation()
    {
       SqlConnection con = new SqlConnection(@"Data Source=localhost;Initial Catalog=WCFTest;Integrated Security=True;Pooling=False");
        con.Open();
        SqlCommand cmd = new SqlCommand("SELECT Processes FROM SaveProcesses", con);
        var result = cmd.ExecuteReader();

        if (result.HasRows)
        {
            con.Close();
            return true;
        }
        else
        {
            con.Close();
            return false;
        }
    }
    }

Im pretty sure I am doing something wrong here as the listbox is getting filled with "loging.cs.servicereference6.Service1Client."

Any ideas on how to implement the wcf?

Answer 1

Well, usually when I'm trying to get data from a Db using WCF, I serialize the object in a string and then at client level I deserialize. From your snippet, I guess you should return a DataTable, serialize it and then deserialize when you have to fill your listbox. What I'd do is this: In your IService interface I declare something like:

[OperationContract]
string GetDataTableFromDB();

In your Service.svc.cs file I'd implement something like:

public string GetDataTableFromDB()
{
    // your code to retrieve from DB the DataTable
    // there are plenty examples here in stackoverflow
    // I will use "retrievedDataTable" name for the retrieved table

    return Serialize<DataTable>(retrievedDataTable);        
}

To be sure that the serialization works correctly, I'd create a class that will contain the DataTable object because JSON might complain if the object that it is trying to serialize does not have the [DataMember] flag. So:

[DataContract]
public class Result
{
    [DataMember]
    public DataTable ResultDataTable { get; set; }
}

In your client, I'd call the method for having the datatable:

public void ShowData2()
{
    try
    {
        ServiceReference6.Service1Client obj6 = new ServiceReference6.Service1Client();
        DataTable table = Deserialize<DataTable>(obj6.SelectSavedProcessInformation());
        if(table != null)
        {
           foreach(DataRow row in table.Rows)
           {
               // fill the listbox
           }
        }

The seirialization and deserialization code that I use is this:

    public class JsonHelper
{
    public static string JsonSerializer<T>(object obj)
    {
        try
        {
            if (obj == null)
                return null;

            using (MemoryStream ms = new MemoryStream())
            {
                DataContractJsonSerializer serializer = new DataContractJsonSerializer(obj.GetType());
                serializer.WriteObject(ms, obj);
                ms.Position = 0;

                using (StreamReader reader = new StreamReader(ms))
                {
                    return reader.ReadToEnd();
                }
            }
        }
        catch { return null; }
    }

    public static T JsonDeserialize<T>(string source)
    {
        try
        {
            if (source == null)
                return default(T);

            using (MemoryStream ms = new MemoryStream(Encoding.Unicode.GetBytes(source)))
            {
                DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(T));
                if (ms.Length == 0)
                    return default(T);

                return (T)serializer.ReadObject(ms);
            }
        }
        catch { return default(T); }
    }
}

I never used DataTable with serialization but I hope it works