Question

Arraylist to hashtable

Asked by: brassmon

I am writing a program that takes data that is entered and stores it in a hashtable, then copies it to an arraylist and puts it in an XML file with serialization... this part of the program is all working fine...

 what I am having trouble with is loading the file back in from the XML file to the arraylist and then to the hashtable... I believe that I am copying back from the XML file to the arraylist just fine, but I don't know how to copy from the arraylist to the hashtable..

 This is a homework program so I am not  looking for the coded answer but just something that can guide me in the right direction... I have been stuck at this point for a while and have every other part of the program working...

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Asked On
2007-10-29 at 16:51:10ID22925825
Tags

arraylist

,

hashtable

,

copy

Topic

C# Programming Language

Participating Experts
1
Points
500
Comments
11

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Answers

 

by: HardiPosted on 2007-10-29 at 17:01:21ID: 20174093

Hi brassmon,
How did you copy from the hashtable into arraylist?

 

by: HardiPosted on 2007-10-29 at 17:03:10ID: 20174101

You can probably use foreach to put each item in the arraylist into hashtable?
foreach (object item in myArrayList)
{
  //add item into your hashtable
}

 

by: brassmonPosted on 2007-10-29 at 17:43:48ID: 20174217

Actually I am wrong, I am taking a class instance and adding it to the arraylist that way for each instance...

I have been trying to use a foreach, but I am confused as to the syntax that I would use...  

 

by: brassmonPosted on 2007-10-29 at 18:40:03ID: 20174366

Looking at this further I believe I have to use foreach and copy each instance into a class instance, and then copy the class instance to the hashtable...  I have two problems with this though..

First:
i have this in a try/catch statement, and for some reason the line here that fills the array list from the stream   causes it to catch every time... I'm not sure why this is...
                FileStream fs = new FileStream(Application.StartupPath + @"\NFLTeams.xml", FileMode.Open);
                SoapFormatter sf = new SoapFormatter();
                theTeams = (ArrayList)(sf.Deserialize(fs));

Second:
I'm not sure how to take the information from the arraylist and put it in the class instance... I think that I would put something like aTeam.teamName, but I don't know what it should equal..

 

by: HardiPosted on 2007-10-29 at 18:56:01ID: 20174416

Hm... I'm not quite sure how you are using the arraylist and hashtable.
1. What error did you get when deserializing it? Is theTeams an arraylist or a class instance?
2. Again, how did you put the class instances into arraylist? We just have to do the reverse right?

Here is an example of serializing/deserializing a class, hope it may help
http://www.devhood.com/tutorials/tutorial_details.aspx?tutorial_id=236

 

by: brassmonPosted on 2007-10-29 at 19:24:16ID: 20174486

When deserializing I don't receive an error, but it goes to the catch... I'm not sure how to tell what the issue is there...

I put the class instances into the arraylist with the line
theTeams.Add(aTeam);
theTeams is the arraylist, and aTeam is the class instance

I am going to meet with my teacher tomorrow afternoon, but I was just hoping to have the program completed prior to the meeting...  He will help me if I can't figure it out... I am going to look through the deserializing information you just sent me... hopefully it helps...  if you would like me to post code I will... maybe that would help...

 

by: HardiPosted on 2007-10-29 at 19:35:16ID: 20174509

In the catch block you can see the message of the exception, right?
When it goes to catch...
try
{
  //deserialize
}
catch(Exception ex)
{
  MessageBox.Show(ex.Message); // <-- what is the message here?
}

You can do this to get each item in the arraylist into a class instance
foreach (object item in theTeams)
{
  aTeam = item;
  //do something with aTeam...
}

I wouldn't mind looking at your code if it's not too long =P
jk, yea just post it here hehe

 

by: brassmonPosted on 2007-10-29 at 19:56:02ID: 20174558

I think you will be able to help me a lot by looking at the code.. I'm sure you will find it very simple.. I think the main problem here is I don't know how to explain my problem very well..

Also, after looking further into things I don't believe the deserialization is the problem.. I think everything is working except I need to add a foreach statement to move things from the arraylist to class instances and then to the hashtable...   I've never used a foreach statement before so I'm having trouble understanding what syntax I should be putting in it...   the foreach statement will be in btnLoad_Click

I really appreciate your help.... I'm sure you have better things to be doing, but its frustrating learning programming :)

namespace NFL
{
    public partial class frmNFL : Form
    {
        public frmNFL()
        {
            InitializeComponent();
        }
        private string teamFile = Application.StartupPath + @"\NFLTeams.xml";
        Hashtable Teams = new Hashtable();
        Team aTeam;
        string teamKey;

        ArrayList theTeams = new ArrayList();

        private void btnExit_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void btnClear_Click(object sender, EventArgs e)
        {
            txtTeam.Clear();
            txtLocation.Clear();
            txtStadium.Clear();
            txtConference.Clear();
            txtDivision.Clear();
        }

        private void btnSaveRecord_Click(object sender, EventArgs e)
        {
            try
            {

                // Create new Class Instance
                aTeam = new Team();
                aTeam.teamName = txtTeam.Text;
                aTeam.location = txtLocation.Text;
                aTeam.stadium = txtStadium.Text;
                aTeam.conference = txtConference.Text;
                aTeam.division = txtDivision.Text;
                teamKey = txtTeam.Text;
                Teams.Add(teamKey.GetHashCode(), aTeam);

                // Add new instance to arraylist
                theTeams.Add(aTeam);
            }
            catch
            {
                MessageBox.Show("Problem Saving Record", "Team Record", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        private void btnRetrieve_Click(object sender, EventArgs e)
        {
            try
            {
                aTeam = new Team();
                teamKey = txtTeam.Text;
                aTeam = (Team)Teams[teamKey.GetHashCode()];
                txtTeam.Text = aTeam.teamName;
                txtLocation.Text = aTeam.location;
                txtStadium.Text = aTeam.stadium;
                txtConference.Text = aTeam.conference;
                txtDivision.Text = aTeam.division;
            }
            catch
            {
                MessageBox.Show("Problem Retrieving Record", "Team Record", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        private void btnLoad_Click(object sender, EventArgs e)
        {
            try
            {
                FileStream fs = new FileStream(teamFile, FileMode.Open);
                SoapFormatter sf = new SoapFormatter();
                theTeams = (ArrayList)(sf.Deserialize(fs));
                fs.Close();


                // now instances must be removed from arraylist and added to hash table using the team as
                // the teamkey for each instance, as they are deserialized
               

                btnRetrieve.Enabled = true;
                btnLoad.Enabled = false;

            }
            catch(Exception ex)
            {
                MessageBox.Show(ex.Message);
            }

        }

        private void btnSaveTable_Click(object sender, EventArgs e)
        {
            FileStream fs = new FileStream(teamFile, FileMode.Create);
            SoapFormatter sf = new SoapFormatter();
            sf.Serialize(fs, theTeams);
            fs.Close();
        }
    }


    [Serializable]
    public class Team
    {
        public string teamName;
        public string location;
        public string stadium;
        public string conference;
        public string division;
    }
}

 

by: HardiPosted on 2007-10-29 at 21:17:28ID: 20174760

Hehe it is frustrating but it is fun once you solve it XD

I think this should do it

.....
// now instances must be removed from arraylist and added to hash table using the team as
// the teamkey for each instance, as they are deserialized
foreach (Object teamObject in theTeams)
{
  string _teamKey = ((Team)teamObject).teamName;
  Teams.Add(_teamKey.GetHashCode(), teamObject); // Add each team to hashtable
}
theTeams.Clear(); // Clear the arraylist
.....

foreach would simply loop over each item in the ArrayList
The foreach loop above can also be written as something like this
for(int i=0; i<theTeams.Length; i++)
{
  Object teamObject = theTeams[i];
  string _teamKey = ((Team)teamObject).teamName;
  Teams.Add(_teamKey.GetHashCode(), teamObject);
}

 

by: brassmonPosted on 2007-10-29 at 21:44:31ID: 20174812

Thank you for your help!  I can't believe that I stared at that code for that long and ended up having 2 lines of code just a little out of whack... but I guess thats usually how it goes :) I did the rest of the program in 10 minutes, and then spent 7 hours on 2 lines... HAHA

 

by: HardiPosted on 2007-10-29 at 21:48:37ID: 20174827

Hahaha yeah that's not unusual.
I recently spent hours on some Perl code that unexpectedly didn't work, only because of 1 newline character! XD
Anyway, glad to have helped you :-D

20120131-EE-VQP-002

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