javascript – 如何使用asp.net添加当前日期的天数

我想将天数添加到当前日期,例如我想输入数字的天数,而不是我选择我想在当前日期添加的日期是指天,周和月,但是当我选择天或周或者它显示日期,但无法在当前日期添加它们
任何人都可以帮助我

protected void TextBoxPreDictDays_TextChanged(object sender,EventArgs E)
        {
            String SELEctPreDictDays = DropDownList1.SELEctedItem.Value;
            String Days1;
            int Result;
            Days1 = TextBoxPreDictedClosing.ToString();
            if (SELEctPreDictDays == "Days")
            {

                Result = Convert.ToInt32(TextBoxPreDictDays.Text) * 1;
                TextBoxPreDictedClosing.Text = Result.ToString();

            }
            else if (SELEctPreDictDays == "Weeks")
            {

                Result = Convert.ToInt32(TextBoxPreDictDays.Text) * 7;
                TextBoxPreDictedClosing.Text = Result.ToString();
            }
            else if (SELEctPreDictDays == "Months")
            {

                Result = Convert.ToInt32(TextBoxPreDictDays.Text) * 30;
                TextBoxPreDictedClosing.Text = Result.ToString();
            }

        }

这是我的设计代码

<asp:TextBox ID="TextBoxPreDictDays" runat="server" 
            ontextchanged="TextBoxPreDictDays_TextChanged"  Width="101px" Height="14px" ></asp:TextBox>
      <asp:DropDownList ID="DropDownList1" runat="server" 
            onSELEctedindexchanged="DropDownList1_SELEctedIndexChanged">
            <asp:ListItem>Days</asp:ListItem>
            <asp:ListItem>Weeks</asp:ListItem>
            <asp:ListItem>Months</asp:ListItem>
        </asp:DropDownList>