Change second dropdown item on selection of first dropdown item

Question

I have two Drop down list.

First drop down is list of months and second is for days.

I want when I select month from first drop down, items of second dropdown change according to selection of first dropdown.

For Example- if I select January from first dropdown, second drop down list become 1 to 31. On selction of february, second drop down list become 1 to 29.

I am trying with this code but not working-

protected void Page_Load(object sender, EventArgs e)
    {
        getDays(dropdownMonth.SelectedValue);

    }

public void getDays(string selectedMonth)
    {
        int i = 0;
         dropdownDays.Items.Clear();
        switch (selectedMonth)
        {
            case "January":
                i = 31;
                break;
            case "February":
                i = 29;
                break;
            case "March":
                i = 31;
                break;
            case "April":
                i = 30;
                break;
            case "May":
                i = 31;
                break;
            case "June":
                i = 30;
                break;
            case "July":
                i = 31;
                break;
            case "August":
                i = 31;
                break;
            case "September":
                i = 30;
                break;
            case "October":
                i = 31;
                break;
            case "November":
                i = 30;
                break;
            case "December":
                i = 31;
                break;
        }

        for (int j = 1; j <= i; j++)
        {
            dropdownDays.Items.Add(j.ToString());
        }
        int Month = DateTime.ParseExact(Convert.ToString(dropdownMonth.SelectedValue), "MMMM", CultureInfo.CurrentCulture).Month;
        int day = Convert.ToInt32(dropdownDays.SelectedValue);
        int year = DateTime.Now.Year;
        DateTime date = new DateTime(year, Month, day);
        lblEndDateValue.Text = String.Format("{0:dd MMMM}", date.AddDays(-1));

if i remove dropdownmonth.items.clear(); from my code then it works but then it adds new days list to previous list on this dropdown.

Is it not submitting (doing nothing) or is it updating the days, but not correct? — Anthony Horne, May 15 '14 at 05:20
it's showing correct dates on selection of month but on selection, it's not selected. it become from starting. — Azhar Shahid, May 15 '14 at 05:23

KarthikManoharan · Accepted Answer · 2014-05-15T06:20:40.407

2

Use the Selected index changed event for first dropdownlist and set autopostback=true for first dropdown

   protected void dropdownMonth_SelectedIndexChanged(object sender, EventArgs e)
   {
       getDays(dropdownMonth.SelectedValue);
   }

set AutoPostBack="true" for dropdownDays also,

  protected void dropdownDays_SelectedIndexChanged(object sender, EventArgs e)
    {
        LabelDays.Text = dropdownDays.SelectedValue;
    }

edited May 15 '14 at 06:20

answered May 15 '14 at 05:22

KarthikManoharan

805
5
12

set AutoPostBack="true" only for dropdownMonth – KarthikManoharan May 15 '14 at 05:36
Remove getDays(dropdownMonth.SelectedValue); from the pageload – KarthikManoharan May 15 '14 at 05:36
try this it will work – KarthikManoharan May 15 '14 at 05:38
it's working but i also want to show that date and month immediate on a label, it's not changing on label – Azhar Shahid May 15 '14 at 05:44
Its working for me try this – KarthikManoharan May 15 '14 at 06:04
what will be on page load ? – Azhar Shahid May 15 '14 at 06:07
Remove all the code from page load sure it will work – KarthikManoharan May 15 '14 at 06:08
it's showing last date of selected month on labeldays.text, not showing selected date from dropdowndays – Azhar Shahid May 15 '14 at 06:13
Use the updated code keep the old code itself additional add this code its working fine for me – KarthikManoharan May 15 '14 at 06:20
it's not working. not doing anything. – Azhar Shahid May 15 '14 at 06:27
let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/52724/discussion-between-karthikmanoharan-and-azhar-shahid) – KarthikManoharan May 15 '14 at 06:28

Jameem · Answer 2 · 2014-05-15T05:35:32.223

0

Try this..You must bind your code inside !ispostback..Otherwise the on each postback the value get reset..

protected void Page_Load(object sender, EventArgs e)
{
  if(!IsPostback)
   {
       //getDays(dropdownMonth.SelectedValue);
   }
}

You can call your function in selectedidexchanged event of month dropdown and set Autopostback=true for the dropdown..I don't think you must call it on pageload..

 protected void dropdownMonth_SelectedIndexChanged(object sender, EventArgs e)
   {
       getDays(dropdownMonth.SelectedValue);
   }

edited May 15 '14 at 05:35

answered May 15 '14 at 05:26

Jameem

1,840
3
15
26

not changing immediate on selection. – Azhar Shahid May 15 '14 at 05:28
1

It should be `!IsPostback` as this won't compile – geedubb May 15 '14 at 05:28
yes i tried it, not working immediate – Azhar Shahid May 15 '14 at 05:29
@AzharShahid I didn't get you friend,Can you please elaborate..Where is the problem and where are you binding the month dropdown? – Jameem May 15 '14 at 05:35
@geedubb typo error friend,thanks for your help.. – Jameem May 15 '14 at 05:36
@AzharShahid Update answer please try,regards.. – Jameem May 15 '14 at 05:39
it's working but i also want to show that date and month immediate on a label, it's not changing on label – Azhar Shahid May 15 '14 at 05:43
Can you please post the code where you setting the label text?] – Jameem May 15 '14 at 05:45
edited my code in question – Azhar Shahid May 15 '14 at 06:00

Change second dropdown item on selection of first dropdown item

2 Answers2