Undo/Redo Functionality in DataGridView c#

Question

I have looked at many topics related to this topic, but I could not find or understand for datagridview table. Finally I made the undo / redo implementation myself using datatable lists. This solution is valid for small tables, I think. I don't know if it will work efficient on tables with lots of data. I will share this solution here. Maybe I will contribute to this website where I learned lots of things. Also I am waiting for comments. Is this solution stupid? or does it work? I need your comments for improvement or give up. Thanx.

Firstly we will add a DataGridView and two buttons named "Undo" and "Redo" to our form

These are codes below;

using System.Windows.Forms;



namespace WindowsFormsApp1

{

    public partial class Form1 : Form

    {

        DataTable dt = null;

        List<DataTable> dtList = new List<DataTable>(); // This list for recording every movements. If we want to do undo/redo, we will get data from this list to dataGridview



        public Form1()

        {
            InitializeComponent();

            dataGridView1.Rows.Add(20);// Add row

            dt = GetDataTableFromDGV(dataGridView1);// make datatable at the beginning

            dtList.Clear();

            dtList.Add(dt);// Beginning data is added to List
        }

        public DataTable GetDataTableFromDGV(DataGridView dgv)// This methot makes a DataTable from DataGridView control.
        {
            var dt = new DataTable();

            foreach (DataGridViewColumn column in dgv.Columns)

            {
             dt.Columns.Add(column.Name);
            }

            object[] cellValues = new object[dgv.Columns.Count];

            foreach (DataGridViewRow row in dgv.Rows)

            {

                for (int i = 0; i < row.Cells.Count; i++)

                {

                    cellValues[i] = row.Cells[i].Value;

                }

                dt.Rows.Add(cellValues);

            }

           return dt;

        }

        int counterUndo = 2;// This counts clicked redo button 

        int dtCount = 0;// This keeps DataTable count

        bool clickedUndo;// This checks Undo button clicked or not.

        private void btn_Undo_Click(object sender, EventArgs e)

        {
            clickedUndo = true;

            dtCount = dtList.Count;

            if (dtCount - counterUndo > -1)

            {
                int undoIndex = dtCount - counterUndo;

                datatablaToDataGrid(dataGridView1, dtList[undoIndex]);

                counterUndo++;
            }
        }

        private void btn_redo_Click(object sender, EventArgs e)

        {
            int redoIndex = dtCount - counterUndo + 2;

            if (counterUndo > 1&&redoIndex< dtCount)

            {
               datatablaToDataGrid(dataGridView1, dtList[redoIndex]);

                counterUndo--;
            }
        }

        public void datatablaToDataGrid(DataGridView dgv, DataTable datatable)// This methot gets data from DataTable to DataGridView control. 

        {
               for (int i = 0; i < datatable.Rows.Count; i++)
                {
                    for (int j = 0; j < datatable.Columns.Count; j++)

                    {
                          dgv.Rows[i].Cells[j].Value = datatable.Rows[i][j].ToString(); 
                    }
                }
        }

        private void dataGridView1_CellValidated(object sender, DataGridViewCellEventArgs e)// This event check if the cell value is change or stay same. 

        {
            DataGridView dgv = (DataGridView)sender;

            int r = e.RowIndex;

            int c = e.ColumnIndex;

            if (dgv.Rows[r].Cells[c].Value != null)

            {
                string dgvResult = dgv.Rows[r].Cells[c].Value.ToString();

                string dtResult = dt.Rows[r][c].ToString();

                if (dgvResult != dtResult)

                {

                    if (clickedUndo)

                    {

                        doWhenClickedUndo(counterUndo, dtList);

                    }

                    dt = GetDataTableFromDGV(dataGridView1);

                    dtList.Add(dt);

                    counterUndo = 2;
               }
            }
        }

        private void doWhenClickedUndo(int _counterUndo, List<DataTable> _dtList)
        {
            if (_counterUndo != 2)

            {
                int f = counterUndo - 2;

                int lastIndex = _dtList.Count - 1;

                int i = lastIndex;

                do
                {
                    _dtList.RemoveAt(i);

                    i--;

                } while (i > lastIndex - f);

               }

            clickedUndo = false;

        }

    }
}

Answer 1

Review

Welcome to Code Review. There are few suggestions as below.

Layout and formatting

Not sure why many newlines between the curly brackets and the method definition, if statements and for statements. For improving readability, those unnecessary newlines can be removed.

Magic numbers and List<DataTable>

I have no idea about why the initial value of counterUndo is set to 2 (in int counterUndo = 2) and why the inequality check if (_counterUndo != 2) is needed in doWhenClickedUndo method. Is the times of undo operation limited in 2? How about the case of more steps the user wants to undo? To solve this issue, I tried to use Stack<DataTable> instead of List<DataTable> so that the Push, Pop and First methods is available (Stack is useful for maintaining the historical sequence like the states of DataTable here). The following code is as an example implementation with Stack class.

public partial class Form1 : Form
{
    Stack<DataTable> dtStack = new Stack<DataTable>();
    int RecordIndex = 0;
    bool UndoRedo = false;

    public Form1()
    {
        InitializeComponent();

        //    Construct Columns
        dataGridView1.ColumnCount = 1;
        dataGridView1.Columns[0].Name = "0";

        dataGridView1.Rows.Add(20);// Add row

        dtStack.Clear();

        dtStack.Push(GetDataTableFromDGV(dataGridView1));
        UpdateBtnStatus();
    }

    public DataTable GetDataTableFromDGV(DataGridView dgv)
    {
        var dt = new DataTable();

        foreach (DataGridViewColumn column in dgv.Columns)
        {
            dt.Columns.Add(column.Name);
        }

        object[] cellValues = new object[dgv.Columns.Count];

        foreach (DataGridViewRow row in dgv.Rows)
        {
            for (int i = 0; i < row.Cells.Count; i++)
            {
                cellValues[i] = row.Cells[i].Value;
            }
            dt.Rows.Add(cellValues);
        }
        return dt;
    }

    public void datatablaToDataGrid(DataGridView dgv, DataTable datatable)
    {
        for (int i = 0; i < datatable.Rows.Count; i++)
        {
            for (int j = 0; j < datatable.Columns.Count; j++)
            {
                dgv.Rows[i].Cells[j].Value = datatable.Rows[i][j].ToString();
            }
        }
    }

    private void UpdateBtnStatus()
    {
        if (RecordIndex == this.dtStack.Count - 1)
            this.btn_Undo.Enabled = false;
        else
            this.btn_Undo.Enabled = true;

        if (RecordIndex == 0)
            this.btn_redo.Enabled = false;
        else
            this.btn_redo.Enabled = true;
    }

    private void btn_Undo_Click(object sender, EventArgs e)
    {
        UndoRedo = true;
        datatablaToDataGrid(dataGridView1, dtStack.ToList()[++RecordIndex]);
        UpdateBtnStatus();
        UndoRedo = false;
    }

    private void btn_redo_Click(object sender, EventArgs e)
    {
        UndoRedo = true;
        datatablaToDataGrid(dataGridView1, dtStack.ToList()[--RecordIndex]);
        UpdateBtnStatus();
        UndoRedo = false;
    }

    private void dataGridView1_CellValidated(object sender, DataGridViewCellEventArgs e)
    {
        UpdateBtnStatus();

        if (UndoRedo)
            return;

        DataGridView dgv = (DataGridView)sender;
        int r = e.RowIndex;
        int c = e.ColumnIndex;
        if (dgv.Rows[r].Cells[c].Value != null)
        {
            string dgvResult = dgv.Rows[r].Cells[c].Value.ToString();
            string dtResult = dtStack.ElementAt(RecordIndex).Rows[r][c].ToString();
            if (dgvResult != dtResult)
            {
                while (RecordIndex > 0)
                {
                    dtStack.Pop();
                    RecordIndex--;
                }

                dtStack.Push(GetDataTableFromDGV(dataGridView1));
            }
        }
        UpdateBtnStatus();
    }
}