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一个dropdownlist的问题

一个dropdownlist的问题# DotNet - 窗口里的风景

j*n2004-09-11 07:09

1 楼

一个dropdownlist,从数据库读取数据动态生成list item.
出现这样一个问题，无论选择了哪一个item,list.SelectedValue永远
等于排在第一的那个item值。
这是可能什么问题造成的？查了一遍又一遍，就是看不出错在哪里了。
哪位牛人来帮我看一下啊？同样的code在其它文件里都跑得好好的。
生成list的code如下：
DropDownList.Items.Clear();
foreach ( ListItem myItem in myListItems)
DropDownList.Items.Add(new ListItem(myItem.Text, myItem.Value));
DropDownList.SelectedIndex = -1;
多谢多谢!

k*i2004-09-11 07:09

2 楼

In which event did you put this code?
If it's a webapp,put it in init but not page load

【在 j****n 的大作中提到】

: 一个dropdownlist,从数据库读取数据动态生成list item.
: 出现这样一个问题，无论选择了哪一个item,list.SelectedValue永远
: 等于排在第一的那个item值。
: 这是可能什么问题造成的？查了一遍又一遍，就是看不出错在哪里了。
: 哪位牛人来帮我看一下啊？同样的code在其它文件里都跑得好好的。
: 生成list的code如下：
: DropDownList.Items.Clear();
: foreach ( ListItem myItem in myListItems)
: DropDownList.Items.Add(new ListItem(myItem.Text, myItem.Value));
: DropDownList.SelectedIndex = -1;

j*n2004-09-11 07:09

3 楼

Thank u for ur reply.
But it is put in an Init_DropDownList event.

【在 k****i 的大作中提到】

: In which event did you put this code?
: If it's a webapp,put it in init but not page load

b*s2004-09-11 07:09

4 楼

你有没有设置dropdownlist的autopostback 为true?

【在 j****n 的大作中提到】

: Thank u for ur reply.
: But it is put in an Init_DropDownList event.

k*i2004-09-11 07:09

5 楼

I would suggest you to move it to Page OnInit() and get rid of the line
'DropDownList.SelectedIndex = -1'(actually this line have no effect on
dropdownlist)

【在 j****n 的大作中提到】

: Thank u for ur reply.
: But it is put in an Init_DropDownList event.

j*n2004-09-11 07:09

6 楼

设置了，但是没有任何作用。

【在 b********s 的大作中提到】

: 你有没有设置dropdownlist的autopostback 为true?

j*n2004-09-11 07:09

7 楼

Thanks, I'll try it tomorrow.

【在 k****i 的大作中提到】

: I would suggest you to move it to Page OnInit() and get rid of the line
: 'DropDownList.SelectedIndex = -1'(actually this line have no effect on
: dropdownlist)

G*T2004-09-11 07:09

8 楼

I would suggest bind data to the dropdownlist in pageload
I did this in my application, never had this problem
seems somthhing is wrong at other places
I would

【在 j****n 的大作中提到】

: Thanks, I'll try it tomorrow.

k*i2004-09-11 07:09

9 楼

R u sure?
data binding in pageload will overwrite the value retrieve from viewstate and
would cause the problem that julyan encountered.Unless you use !IsPostBack

【在 G**T 的大作中提到】

:
: I would suggest bind data to the dropdownlist in pageload
: I did this in my application, never had this problem
: seems somthhing is wrong at other places
: I would

G*T2004-09-11 07:09

10 楼

and
ur right, use NOT isPostBack
line

【在 k****i 的大作中提到】

: R u sure?
: data binding in pageload will overwrite the value retrieve from viewstate and
: would cause the problem that julyan encountered.Unless you use !IsPostBack

M*k2004-09-11 07:09

11 楼

en, i guess your solution is correct.
the re-initialize of dropdownlist in Page_Load
overwrite the viewstate, so he can't get selectedValue
in the event.

【在 k****i 的大作中提到】

: R u sure?
: data binding in pageload will overwrite the value retrieve from viewstate and
: would cause the problem that julyan encountered.Unless you use !IsPostBack