Question

无法弄清楚为什么我的程序不会使用循环填充 DropDownList 。

到目前为止，我已尝试过这两种情况：

'Fill in the year box from current year to 100 years ago.
'(Safe to assume no one over 100 will be signing up for site)

Dim CurYear As Integer = Date.Now.Year
Dim CurYearMinus100 As Integer = CurYear - 100
Dim Index As Integer = 0

Do While CurYear >= CurYearMinus100
    DropDownListYear.Items.Insert(Index, CurYear)
    Index += 1
    CurYear -= 1
Loop

我也尝试使用.Add()功能而不是插入：

Dim CurYear As Integer = Date.Now.Year
Dim CurYearMinus100 As Integer = CurYear - 100

Do While CurYear >= CurYearMinus100
    DropDownListYear.Items.Add(Index)
    CurYear -= 1
Loop

Answer 1

不确定为什么需要Index，但此代码可以使用：

Dim CurYear As Integer = Date.Now.Year
Dim CurYearMinus100 As Integer = CurYear - 100

Do While CurYear >= CurYearMinus100
    DropDownListYear.Items.Add(New ListItem(CurYear.ToString(), CurYear.ToString()))
    CurYear -= 1
Loop

Answer 2

我个人是 For...Next 语句的粉丝，其中包含递减的 Step 参数。

可选。数字表达式。计数器的数量每次循环都会增加。

你的例子是：

Dim currentYear = Date.Now.Year

For year = currentYear To currentYear - 100 Step -1

   DropDownListYear.Items.Add(New ListItem(year.ToString(), year.ToString()))

Next

Answer 3

替换它：

DropDownListYear.Items.Insert(Index, CurYear)

使用：

DropDownListYear.Items.Insert(Index, new ListItem(CurYear.ToString(), CurYear.ToString()))

使用循环将整数填充到下拉列表

3 个答案: