maintain student scores c#

Question

jluna 0 Newbie Poster

10 Years Ago

Hello, I'm having trouble getting a part of this program to work... the update student part is supposed to update/edit student's scores.
When i run the program i cant get the bttnUpdate to work in the frmMaintStudentScores.cs. can someone help me fix it?
the other parts of the program are working.

frmUpdateStudentScores.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication4
{
    public partial class frmUpdateStudentScores : Form
    {
        public static Dictionary<string, List<int>> tmpStudents;
        BindingSource bs = new BindingSource();
        public static int selected;

        public frmUpdateStudentScores()
        {
            InitializeComponent();
        }

        private void frmUpdateStudentScores_Load(object sender, EventArgs e)
        {
            tmpStudents = frmMaintStudentScores.students.ToDictionary(p => p.Key, p => p.Value.ToList());

        }

        private void frmUpdateStudentScores_Activated(object sender, EventArgs e)
        {
            txtName.Text = tmpStudents.Keys.ElementAt(frmMaintStudentScores.selected);
            bs.DataSource = tmpStudents.Values.ElementAt(frmMaintStudentScores.selected);
            lbxScores.DataSource = bs;
            lbxScores.Focus();
        }

        private void bttnAdd_Click(object sender, EventArgs e)
        {
            Form addScore = new frmAddScore();
            addScore.ShowDialog();
            bs.ResetBindings(false);
        }

        private void BttnOk_Click(object sender, EventArgs e)
        {
            frmMaintStudentScores.students = tmpStudents;
            this.Close(); 
        }

        private void bttnRemove_Click(object sender, EventArgs e)
        {

            tmpStudents.Values.ElementAt(frmMaintStudentScores.selected).RemoveAt(lbxScores.SelectedIndex);
            bs.ResetBindings(false);
        }

        private void bttnUpdate_Click(object sender, EventArgs e)
        {
            selected = lbxScores.SelectedIndex;
            Form updateScore = new frmUpdateScore();
            updateScore.ShowDialog();
            bs.ResetBindings(false);
        }


        private void bttnClreaScores_Click(object sender, EventArgs e)
        {
            tmpStudents.Values.ElementAt(frmMaintStudentScores.selected).RemoveRange(
               0, tmpStudents.Values.ElementAt(frmMaintStudentScores.selected).Count);
            bs.ResetBindings(false);
        }

    }
}

main form: frmMaintStudentScores.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication4
{
    public partial class frmMaintStudentScores : Form
    {
        public static Dictionary<string, List<int>> students = new Dictionary<string, List<int>>();
        public static int selected;

        public frmMaintStudentScores()
        {
            InitializeComponent();
        }

      //  private frmMaintStudentScores parentForm;

        private void frmStudentScores_Load(object sender, EventArgs e)
        {

            students.Add("Peter Cornell", new List<int> { 20, 30, 50 });
            students.Add("Joe Whatsits", new List<int> { 24, 44, 34 });
            students.Add("Jane Harris", new List<int> { 64, 43, 65 });

            AddToListbox();

        }

        private void AddToListbox()
        {
            foreach (var student in students)
            {
                StringBuilder sb = new StringBuilder();
                sb.Append(student.Key.ToString());
                sb.Append(" - ");
                for (int i = 0; i < student.Value.Count; i++)
                {
                    sb.Append(student.Value[i]);
                    if (i != student.Value.Count - 1)
                    {
                        sb.Append(", ");
                    }
                }
                lbxStudents.Items.Add(sb);
                lbxStudents.SetSelected(0, true);
                UpdateInfo();
            }
        }

        private void UpdateInfo()
        {
            try
            {

                txtScoreTotal.Text = students.Values.ElementAt(lbxStudents.SelectedIndex).Sum().ToString();
                txtScoreCount.Text = students.Values.ElementAt(lbxStudents.SelectedIndex).Count.ToString();
                txtAverage.Text = Math.Round(students.Values.ElementAt(lbxStudents.SelectedIndex).Average()).ToString();
            }
            catch (Exception)
            {
                txtScoreTotal.Text = "";
                txtScoreCount.Text = "";
                txtAverage.Text = "";
            }
        }

        private void lbxStudents_SelectedIndexChanged(object sender, EventArgs e)
        {
            UpdateInfo();
        }

        private void bttnAddNew_Click(object sender, EventArgs e)
        {
            Form addNewStudent = new frmAddNewStudent();
            addNewStudent.ShowDialog();
            lbxStudents.Items.Clear();
            AddToListbox();
        }

        private void btnUpdate_Click(object sender, EventArgs e)
        {

            Form updateScores = new frmUpdateStudentScores();
            int index = lbxStudents.SelectedIndex;
            if (lbxStudents.Items.Count > 0)
            {
                updateScores.ShowDialog();
            }

            lbxStudents.Items.Clear();
            AddToListbox();

        }

        private void bttnDelete_Click(object sender, EventArgs e)
        {
            students.Remove(students.Keys.ElementAt(lbxStudents.SelectedIndex));
            lbxStudents.Items.Clear();
            AddToListbox();
            if (students.Count == 0)
            {
                txtScoreTotal.Text = "";
                txtScoreCount.Text = "";
                txtAverage.Text = "";
            }
        }

         private void frmStudentScores_Activated(object sender, EventArgs e)
        {
            UpdateInfo();
        }

    }
}

}}

.net:c#

Edited 10 Years Ago by jluna

2 Contributors
2 Replies
2K Views
4 Years Discussion Span
Latest Post 5 Years Ago Latest Post by lixasaj321

lixasaj321 commented: can you send me the full code asap please +0

Dani AI

Generated 11 Months Ago

the update dialog never learns which student was selected. You create the dialog, but you do not set frmMaintStudentScores.selected anywhere, and the update form relies on that value. Also, using ElementAt(...) on a Dictionary assumes a stable order that is not guaranteed. Two quick paths:

Minimal change (uses your existing static field)

// frmMaintStudentScores.cs
private void btnUpdate_Click(object sender, EventArgs e)
{
    if (lbxStudents.SelectedIndex < 0) return;

    // Tell the update form which student index to use
    frmMaintStudentScores.selected = lbxStudents.SelectedIndex;

    using (var dlg = new frmUpdateStudentScores())
    {
        dlg.ShowDialog(this);
    }

    lbxStudents.Items.Clear();
    AddToListbox();
}

And in the update form, guard against no selection:

private void frmUpdateStudentScores_Activated(object sender, EventArgs e)
{
    if (frmMaintStudentScores.selected < 0) return;

    var idx = frmMaintStudentScores.selected;
    txtName.Text = tmpStudents.Keys.ElementAt(idx);
    bs.DataSource = tmpStudents.Values.ElementAt(idx);
    lbxScores.DataSource = bs;
    lbxScores.Focus();
}

Better pattern (pass a key, stop relying on dictionary order and statics)

// frmMaintStudentScores.cs
private void btnUpdate_Click(object sender, EventArgs e)
{
    if (lbxStudents.SelectedIndex < 0) return;
    var key = students.Keys.ElementAt(lbxStudents.SelectedIndex);
    using (var dlg = new frmUpdateStudentScores(key))
        dlg.ShowDialog(this);

    lbxStudents.Items.Clear();
    AddToListbox();
}

// frmUpdateStudentScores.cs
private readonly string studentKey;
public frmUpdateStudentScores(string key) { InitializeComponent(); studentKey = key; }

private void frmUpdateStudentScores_Activated(object sender, EventArgs e)
{
    txtName.Text = studentKey;
    bs.DataSource = tmpStudents[studentKey];
    lbxScores.DataSource = bs;
}

Small cleanups that will save you crashes:

Check lbxScores.SelectedIndex >= 0 before RemoveAt(...).
Move lbxStudents.SetSelected(0, true); outside the foreach in AddToListbox().

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jluna 0 Newbie Poster · Answer 1 · 2016-05-22T19:21:05+00:00

I actually got the update button to work..something i had made a mistake on in the designer.. ha. Now I'm having trouble displaying a student i want to update in the student update scores form.

should look something like this:

lixasaj321 0 Newbie Poster · Answer 2 · 2020-10-17T14:51:53+00:00

lixasaj321 0 Newbie Poster

5 Years Ago

Please send me the full source code ASAP please