C#按错误顺序从文本框中读取每个文本

所以我尝试将坐标从文本框加载到双倍列表中。我已经编辑了他们的TabIndex,所以它们是有序的,但当我尝试加载数字时,它正在读取一些奇怪的odrer中的文本框。2->4->8->7->5->6->3->有人能帮我吗?sur\u x和sur\u y是列表的名称。

    public Boolean Nacitanie_hodnot()
    {
        // premazanie listov a vlozenie prvej hodnoty
        sur_x.Clear();
        sur_y.Clear();
        sur_x.Add(0);
        sur_y.Add(0);

        int i = 1;
        // nacitanie hodnot
        /*Ax = double.Parse(suradnica_Ax.Text, CultureInfo.InvariantCulture.NumberFormat);
        Ay = double.Parse(suradnica_Ay.Text, CultureInfo.InvariantCulture.NumberFormat);
        Bx = double.Parse(suradnica_Bx.Text, CultureInfo.InvariantCulture.NumberFormat);
        By = double.Parse(suradnica_By.Text, CultureInfo.InvariantCulture.NumberFormat);

        Cx = double.Parse(suradnica_Cx.Text, CultureInfo.InvariantCulture.NumberFormat);
        Cy = double.Parse(suradnica_Cy.Text, CultureInfo.InvariantCulture.NumberFormat);
        Dx = double.Parse(suradnica_Dx.Text, CultureInfo.InvariantCulture.NumberFormat);
        Dy = double.Parse(suradnica_Dy.Text, CultureInfo.InvariantCulture.NumberFormat);*/
        foreach (Control control in suradnice_vrcholov.Controls)
        {
            if ((control is TextBox) && (control.Text == "Zadaj"))
            {
                return false;
            }

            else if ((control is TextBox) && ((i % 2) != 0))
            {
                sur_x.Add(double.Parse(control.Text, CultureInfo.InvariantCulture.NumberFormat));
                i++;
            }

            else if ((control is TextBox) && ((i % 2) == 0))
            {
                sur_y.Add(double.Parse(control.Text, CultureInfo.InvariantCulture.NumberFormat));
                i++;
            }
        }
        return true;
    }