Find Max for each row in ASP.Net GridView dynamic columns using C#

I have 2 GridView grdvieMarks for add online questionAnssheet and GridviewMaxmarks for adding maxmarks for each question.

I know only first 2 columns of gridviewmarks, id and name of each row, and other columns count dynamic and these 2 columns are also dynamic. On save button i want to find each id, admission number and max marks of that question

I get data in dataset, only its 2 column (id and emplyeename) name are same, otherwise all dynamic (column name questionno, and value is its answer).

I firstly bind it in gridviewmarks, and then i create another GridView to enter maxmarks of each question.

On save i want to find id, questionno, ans(value of each question), maxmarks entered.

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate>
        <asp:GridView ID="grdvieMarks" runat="server"></asp:GridView>
        <div id="dimxmatks" style="overflow: auto">
            <asp:GridView ID="GridviewMaxmarks" runat="server" AutoGenerateColumns="false" OnRowDataBound="GridviewMaxmarks_RowDataBound"></asp:GridView>
        </div>
        <asp:Button ID="btnsave" runat="server" Text="Save" OnClick="btnsave_Click" />
    </ContentTemplate>

    <Triggers>
        <asp:PostBackTrigger ControlID="btnsave" />
    </Triggers>
</asp:UpdatePanel>

rdvieMarks.DataSource = dsCustomers;
grdvieMarks.DataBind();
{
    GridviewMaxmarks.Columns.Clear();
    DataTable dt = new DataTable();
    int cols = Convert.ToInt32(dsCustomers.Tables[0].Columns.Count - 2);
    int rows = Convert.ToInt32(dsCustomers.Tables[0].Rows.Count);
    for (int i = 0; i < cols; i++)
    {
        TemplateField field = new TemplateField();
        field.HeaderText = dsCustomers.Tables[0].Columns[i + 2].ColumnName.ToString();

        GridviewMaxmarks.Columns.Add(field);
    }

    if (rows > 0)
    {
        dt.Rows.Add();
    }

    GridviewMaxmarks.DataSource = dt;
    GridviewMaxmarks.DataBind();

DataTable dt2 = new DataTable();
{
    for (int i = 0; i < GridviewMaxmarks.Columns.Count; i++)
    {
        dt.Columns.Add("column" + i.ToString());
    }
    foreach (GridViewRow row in GridviewMaxmarks.Rows)
    {
        DataRow dr2 = dt.NewRow();
        for (int j = 0; j < GridviewMaxmarks.Columns.Count; j++)
        {
            dr2["column" + j.ToString()] = row.Cells[j].Text;
        }
        dt.Rows.Add(dr2);
    }
}

protected void btnsave_Click(object sender, EventArgs e)
{
    for (int i = 0; i < grdvieMarks.Rows.Count; i++)
    {
        clsQuestionAnsSheet obj = new clsQuestionAnsSheet();

        obj.AdmissionNo = grdvieMarks.Rows[i][0].Text;
        for (int j = 2; j < grdvieMarks.Columns.Count; j++)
        {
            string columnname = grdvieMarks.Columns[j].ToString();
            obj.Subject_id = "1";
            obj.Session = Session["2021-2022"].ToString();
            obj.UserId = Session["id"].ToString();
            obj.QuestionNo = columnname;
        }
    }
}

protected void GridviewMaxmarks_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        for (int i = 0; i < GridviewMaxmarks.Columns.Count; i++)
        {
            int rowID = e.Row.RowIndex;
            TextBox textbox = new TextBox();
            //textbox.CssClass = "form-control input-sm";
            textbox.ID = GridviewMaxmarks.Columns[i].ToString();
            RegularExpressionValidator regex = new RegularExpressionValidator();
            regex.ID = "Regex" + GridviewMaxmarks.Columns[i].ToString();
            regex.ControlToValidate = textbox.ID;
            regex.Display = ValidatorDisplay.Dynamic;
            regex.SetFocusOnError = true;
            regex.ValidationExpression = "^([0-9]\\d*)(\\.\\d{1,2})?$";
            regex.ErrorMessage = "INvalid Value";

            e.Row.Cells[i].Controls.Add(textbox);
            e.Row.Cells[i].Controls.Add(regex);
        }
    }
}