如何从第一个下拉列表中选择第二个下拉项目 [英] how to change second drop down item on selection from first drop down list

问题描述

我正在使用面板。

我有两个下拉列表。一个是月，另一个是几天。

I have two drop down list. one is for month and another is for days.

问题1

我每当我从第一个下拉菜单中选择月份，根据月份的选择，不会有第二天下降的天数。

I want whenever I select month from first drop down, no of days in second drop down become according to selection of month.

举个例子 - 如果我选择1月第二个下拉列表从1到31.如果我选择二月第二个下拉列表变为1到29等等。

For Example- if I am selecting "January" then second drop down list become from 1 to 31. If I am selecting "Febuary" second drop down list become 1 to 29 and so on..

Question2

我从下拉列表中选择startdate，我在标签中显示最后一个日期。

I am selecting startdate from dropdowns and I am showing last date in label.

例如 - 如果我从第一个下拉菜单中选择1月。日期1从第二个下拉列表。

然后Laabel1.text成为最后一个日期，即31年12月31日。

For example- If I am selecting "January" from first dropdown. Date "1" from second dropdown.
Then Laabel1.text become last date i.e. 31 december.

我的面板的屏幕截图是 -

我正在尝试这个但是不起作用。

I am trying this but it's not working.

public void getDaysOnMonthSelection(string Month)
    {
        int i=0;
        switch (Month)
        {
            case "January":
                i = 31;
                break;
            case "Febuary":
                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;
        }
        dropdownDays.Items.Clear();
        for (int j = 1; j <= i; j++)
        {
            dropdownDays.Items.Add(j.ToString());
        }
        lblEndDateValue.Text = dropdownDays.Text + "  " + dropdownMonth.Text;

    }

推荐答案

答案是你必须删除一行代码 -

For first answer you have to remove one line of your code-

删除此行 -

dropdownDays.Items.Clear();

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