C# WinApp DataGridView ต้องการใส่การคำนวณใน DataGridView ครับ

private void aLS_F_711DataGridView_CellEndEdit(object sender, DataGridViewCellEventArgs e)
        {
            DataGridView dgv = sender as DataGridView;
            if (dgv[1, e.RowIndex].Value == null || string.IsNullOrEmpty(dgv[1, e.RowIndex].Value.ToString()))
            {
                dgv[1, e.RowIndex].Value = f711Item;

            }
            if (e.ColumnIndex == 3)
            {
                string value = dgv.Rows[e.RowIndex].Cells[e.ColumnIndex].Value.ToString();

                if (value.StartsWith("="))
                {
                    string expression = value.Substring(1); // เอาเฉพาะส่วนที่ต้องการคำนวณ

                    // คำนวณ
                    DataTable table = new DataTable();
                    var result = table.Compute(expression, "");
                    MessageBox.Show(result.ToString());
                    dgv[3, e.RowIndex].Value = result;
                }
            }
        }

     #region _DataGridViewCalColumn
        public class DataGridViewCalColumn : DataGridViewColumn
        {
            public DataGridViewCalColumn()
                : base(new DataGridViewCalCell())
            {
            }

            public override DataGridViewCell CellTemplate
            {
                get { return base.CellTemplate; }
                set
                {
                    if (!(value is DataGridViewCalCell))
                        throw new InvalidCastException("Must be a DataGridViewCalCell");

                    base.CellTemplate = value;
                }
            }
        }

        internal class DataGridViewCalCell : DataGridViewTextBoxCell
        {
            public override void InitializeEditingControl(int rowIndex, object initialFormattedValue, DataGridViewCellStyle dataGridViewCellStyle)
            {
                base.InitializeEditingControl(rowIndex, initialFormattedValue, dataGridViewCellStyle);
            }

            protected override void OnLeave(int rowIndex, bool throughMouseClick)
            {
                base.OnLeave(rowIndex, throughMouseClick);

                if ((!object.ReferenceEquals(this.Value, DBNull.Value)) && (this.Value != null))
                {
                    string value = this.Value.ToString();
                    string expression = (value.StartsWith("=")) ? value.Substring(1) : value; // เอาเฉพาะส่วนที่ต้องการคำนวณ

                    var result = new DataTable().Compute(expression, "");

                   this.Value =result.ToString();
                

               }
                if (DataGridView != null)DataGridView.EndEdit();

            }

            public override Type EditType => typeof(DataGridViewCalEdit);
            public override Type ValueType => typeof(string);
        }

      internal  class DataGridViewCalEdit : TextBox, IDataGridViewEditingControl
        {
            private DataGridView dataGridViewControl;
            private bool valueIsChanged = false;
            private int rowIndexNum;

            public object EditingControlFormattedValue
            {
                get => Text;
                set
                {
                    if (value is string str)
                        Text = str;
                }
            }

            public object GetEditingControlFormattedValue(DataGridViewDataErrorContexts context) => Text;

            public void ApplyCellStyleToEditingControl(DataGridViewCellStyle dataGridViewCellStyle) => Font = dataGridViewCellStyle.Font;

            public int EditingControlRowIndex
            {
                get => rowIndexNum;
                set => rowIndexNum = value;
            }

            public bool EditingControlWantsInputKey(Keys key, bool dataGridViewWantsInputKey)
            {
                switch (key & Keys.KeyCode)
                {
                    case Keys.Left:
                    case Keys.Up:
                    case Keys.Down:
                    case Keys.Right:
                    case Keys.Home:
                    case Keys.End:
                    case Keys.PageDown:
                    case Keys.PageUp:
                        return true;
                    default:
                        return false;
                }
            }

            public void PrepareEditingControlForEdit(bool selectAll)
            {
            }

            public bool RepositionEditingControlOnValueChange => false;

            public DataGridView EditingControlDataGridView
            {
                get => dataGridViewControl;
                set => dataGridViewControl = value;
            }

            public bool EditingControlValueChanged
            {
                get => valueIsChanged;
                set => valueIsChanged = value;
            }

            public Cursor EditingControlCursor => Cursor;

            Cursor IDataGridViewEditingControl.EditingPanelCursor => EditingControlCursor;

            protected override void OnTextChanged(EventArgs e)
            {
                valueIsChanged = true;
                EditingControlDataGridView.NotifyCurrentCellDirty(true);
                base.OnTextChanged(e);
            }
        }
        #endregion

    #region _DataGridViewCal_NewColumn
      /// <summary>
      /// Hosts a collection of DataGridViewTextBoxCell cells.
      /// </summary>
      public class DataGridViewCal_NewColumn : DataGridViewColumn
    {

        // public enum PathType { directory, file };
        //public PathType pathtype = PathType.file;

        public DataGridViewCal_NewColumn()
            : base(new DataGridViewCal_NewCell())
        {

        }
        private bool _showbutton = true;
        [System.ComponentModel.Browsable(true)]
        [System.ComponentModel.Category("TOR Setting")]
        [System.ComponentModel.Description("Disible/Enable Button")]
        public bool ShowButton
        {
            get { return _showbutton; }
            set
            {
                _showbutton = value;
            }
        }

        public override object Clone()
        {
            var clm = base.Clone() as DataGridViewCal_NewColumn;
            DataGridViewCal_NewColumn xxx = base.Clone() as DataGridViewCal_NewColumn;
            if (clm != null)
            {
                clm.ShowButton = _showbutton;

            }
            return clm;

        }

        public override DataGridViewCell CellTemplate
        {
            get
            {
                return base.CellTemplate;
            }
            set
            {
                if (null != value &&
                    !value.GetType().IsAssignableFrom(typeof(DataGridViewCal_NewCell)))
                {
                    throw new InvalidCastException("must be a DataGridViewCal_NewCell");
                }
                base.CellTemplate = value;
            }
        }
    }

    /// <summary>
    /// Displays editable text information in a DataGridView control. Uses
    /// PathEllipsis formatting if the column is smaller than the width of a
    /// displayed filesystem path.
    /// </summary>
    public class DataGridViewCal_NewCell : DataGridViewTextBoxCell
    {
        Button browseButton;
        Dictionary<Color, SolidBrush> brushes = new Dictionary<Color, SolidBrush>();
        protected virtual SolidBrush GetCachedBrush(Color color)
        {
            if (this.brushes.ContainsKey(color))
                return this.brushes[color];
            SolidBrush brush = new SolidBrush(color);
            this.brushes.Add(color, brush);
            return brush;
        }


        protected virtual bool RightToLeftInternal
        {
            get
            {
                return this.DataGridView.RightToLeft == RightToLeft.Yes;
            }
        }

        protected override void OnLeave(int rowIndex, bool throughMouseClick)
        {
            base.OnLeave(rowIndex, throughMouseClick);
            browseButton.Hide();
        }
        protected override void OnEnter(int rowIndex, bool throughMouseClick)
        {
            browseButton.Hide();
            base.OnEnter(rowIndex, throughMouseClick);
            DataGridViewCal_NewColumn calColumn = (DataGridViewCal_NewColumn)this.DataGridView.Columns[ColumnIndex];

            if (RowIndex < 0 || !calColumn.ShowButton) return;

            Rectangle Loc;
            int Wid;
            Loc = this.DataGridView.GetCellDisplayRectangle(ColumnIndex, RowIndex, false);
            Wid = this.DataGridView.CurrentCell.Size.Width;
            browseButton.Location = new Point(Loc.X - 25 + Wid, Loc.Y - 4);
            browseButton.Height = this.DataGridView.CurrentCell.Size.Height + 4;
            browseButton.Width = browseButton.Height;

            if (!this.DataGridView.Controls.Contains(browseButton))
                this.DataGridView.Controls.Add(browseButton);
            browseButton.Show();

        }

        public bool ShowFocusCues
        {
            get { return true; }
        }

        protected bool ApplyVisualStylesToHeaders
        {
            get
            {
                if (Application.RenderWithVisualStyles)
                {
                    return this.DataGridView.EnableHeadersVisualStyles;
                }
                return false;
            }
        }


        public DataGridViewCal_NewCell()
            : base()
        {

            browseButton = new Button();
            // browseButton.FlatStyle = FlatStyle.Flat;
            browseButton.FlatAppearance.BorderSize = 0;
            browseButton.Size = new Size(30, 25);
            browseButton.ImageAlign = ContentAlignment.MiddleCenter;
            browseButton.FlatAppearance.MouseDownBackColor = Color.Transparent;
            browseButton.FlatAppearance.MouseOverBackColor = Color.Transparent;
            browseButton.BackColor = Color.Transparent;
            browseButton.Text = "...";
            browseButton.Hide();

            browseButton.Click += (o, e) => {
                DataGridViewCal_NewColumn filePathColumn = (DataGridViewCal_NewColumn)this.DataGridView.Columns[ColumnIndex];
                EditCell cell = new EditCell();
                if (cell.ShowDialog() == DialogResult.OK)
                {
                    if (!string.IsNullOrEmpty(cell.Value))
                    {
                        base.Value = cell.Value;

                    }
                }
            };

        }

    }

    #endregion

    internal partial class EditCell : Form
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.label1 = new System.Windows.Forms.Label();
            this.txt = new System.Windows.Forms.TextBox();
            this.btnOK = new System.Windows.Forms.Button();
            this.btnCancel = new System.Windows.Forms.Button();
            this.SuspendLayout();
            // 
            // label1
            // 
            this.label1.AutoSize = true;
            this.label1.Location = new System.Drawing.Point(19, 9);
            this.label1.Margin = new System.Windows.Forms.Padding(6, 0, 6, 0);
            this.label1.Name = "label1";
            this.label1.Size = new System.Drawing.Size(116, 25);
            this.label1.TabIndex = 0;
            this.label1.Text = "Cell Value:";
            // 
            // txt
            // 
            this.txt.Location = new System.Drawing.Point(88, 49);
            this.txt.Margin = new System.Windows.Forms.Padding(6);
            this.txt.Name = "txt";
            this.txt.Size = new System.Drawing.Size(386, 31);
            this.txt.TabIndex = 1;
            this.txt.KeyDown += new System.Windows.Forms.KeyEventHandler(this.txt_KeyDown);
            // 
            // btnOK
            // 
            this.btnOK.DialogResult = System.Windows.Forms.DialogResult.OK;
            this.btnOK.Location = new System.Drawing.Point(387, 115);
            this.btnOK.Margin = new System.Windows.Forms.Padding(6);
            this.btnOK.Name = "btnOK";
            this.btnOK.Size = new System.Drawing.Size(150, 44);
            this.btnOK.TabIndex = 2;
            this.btnOK.Text = "OK";
            this.btnOK.UseVisualStyleBackColor = true;
            this.btnOK.Click += new System.EventHandler(this.btnOK_Click);
            // 
            // btnCancel
            // 
            this.btnCancel.DialogResult = System.Windows.Forms.DialogResult.Cancel;
            this.btnCancel.Location = new System.Drawing.Point(24, 115);
            this.btnCancel.Margin = new System.Windows.Forms.Padding(6);
            this.btnCancel.Name = "btnCancel";
            this.btnCancel.Size = new System.Drawing.Size(150, 44);
            this.btnCancel.TabIndex = 3;
            this.btnCancel.Text = "Cancel";
            this.btnCancel.UseVisualStyleBackColor = true;
            this.btnCancel.Click += new System.EventHandler(this.btnCancel_Click);
            // 
            // EditCell
            // 
            this.AcceptButton = this.btnOK;
            this.AutoScaleDimensions = new System.Drawing.SizeF(12F, 25F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.CancelButton = this.btnCancel;
            this.ClientSize = new System.Drawing.Size(552, 174);
            this.Controls.Add(this.btnCancel);
            this.Controls.Add(this.btnOK);
            this.Controls.Add(this.txt);
            this.Controls.Add(this.label1);
            this.Font = new System.Drawing.Font("Microsoft Sans Serif", 15.75F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(222)));
            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedToolWindow;
            this.Margin = new System.Windows.Forms.Padding(6);
            this.Name = "EditCell";
            this.StartPosition = System.Windows.Forms.FormStartPosition.CenterParent;
            this.Text = "Edit Cell Value";
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private System.Windows.Forms.Label label1;
        private System.Windows.Forms.TextBox txt;
        private System.Windows.Forms.Button btnOK;
        private System.Windows.Forms.Button btnCancel;

        public EditCell()
        {
            InitializeComponent();
        }

        public string Value
        {
            get { return txt.Text; }
            set { txt.Text = value; }
        }

        private void btnOK_Click(object sender, System.EventArgs e)
        {
            Cal();
        }

        private void btnCancel_Click(object sender, EventArgs e)
        {
            Close();
        }

        private void txt_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Enter) Cal();
        }
        void Cal()
        {
            string expression = txt.Text;
            if (txt.Text.StartsWith("="))
            {
                expression = txt.Text.Substring(1); 

            }
            // คำนวณ
            DataTable table = new DataTable();
            var result = table.Compute(expression, "");
            Value = result.ToString();
            Close();
        }
    }