如何让第一个组合框输入空白？ [英] How to make first combo box entry blank?
问题描述
使用DropDownList在HTML中创建select / option标签如何制作第一个选项
是一个空白字符串？
我有可选值的字段。目前我正在通过
填充DropDownList来查询表中的选项列表。但是表格不应该有一个空行。
几种可能性：
1）使用UNION查询。我在MS Access中使用组合框完成了这个操作，并且union的第一个
成员返回一行。我不记得
的SQL语法返回不是来自表的单行。任何人都知道怎么做？
2）在没有绑定结果集的情况下填充CodeBehind中的DropDownList。只需添加一个
空白行，然后对具有实际行的数据集进行foreach并添加所有行。
3）其他一些方法？
＃1要求你的数据层知道演示文稿，这样就可以了。
＃ 2工作正常，并会用oldskool纯粹主义者和php
孩子给你积分，但与...相比这是额外的工作...
＃3从数据库中获取数据集并在其中加入一行额外的行
绑定之前：
private void PopulateFamilyList（）
{
DataSet ds = Family.List（）;
ds.Tables [0] .Rows.InsertAt（ds.Tables [0] .NewRow（），0）;
DataView dv = ds.Tables [0] .DefaultView;
dv.Sort = Family.Columns.FamilyName;
selFamilyID.DataSource = dv;
selFamilyID.DataValueField = Family.Columns.FamilyID;
selFamilyID.DataTextField = Family.Columns.FamilyName;
selFami lyID.DataBind（）;
}
祝你好运！
Jason Kester
外籍软件咨询服务
http://www.expatsoftware.com/
---
获取自己的旅游博客，包括行程地图和照片！
http://www.blogabond.com/
数据绑定后， DropDownList.Items.Inser（0，""）
" Randall Parker" < NOtechieSPAMpundit_please @ future_avoidjunk_pundit .com>
在消息新闻中写道：％2 **************** @ tk2msftngp13.phx.gbl ...
使用DropDownList在HTML中创建select / option标签如何使
第一个选项
是一个空白字符串？
我有可选值的字段。目前我正在通过
填充
DropDownList来查询表中的选项列表。但桌子不应该有一个
空白行。
有几种可能性：
1 ）使用UNION查询。我已经在MS Access中使用组合框和
第一个
成员返回单行。我不记得SQL语法
for
返回一个不是来自表的单行。任何人都知道怎么做？
2）在没有绑定结果集的情况下填充CodeBehind中的DropDownList。
只需添加一个
空白行然后在具有实际行的数据集上做一个foreach，并且
添加它们。
3）其他一些方法？
Siva M写道：数据绑定后，DropDownList.Items.Inser（0，""）
我会建议不要这样做。 DataBound控件有时会在绑定后修改它们后再翻转。
Jason Kester
外籍软件咨询服务
http://www.expatsoftware.com/
Using DropDownList to create select/option tags in HTML how to make the first option
be a blank string?
I have fields with optional values. Currently I''m populating the DropDownList by
querying out a list of choices from a table. But the table shouldn''t have a blank row.
A couple of possibilities:
1) Use a UNION query. I''ve done this in MS Access with combo boxes and the first
member of the union returns a single row. I can''t remember the SQL syntax for
returning a single row that is not from a table though. Anyone know how?
2) Populate the DropDownList in CodeBehind without a bind of a result set. Just add a
blank row and then do a foreach on the dataset that has the real rows and add all them.
3) Some other approach?
#1 requires your datalayer to know about presentation, so that''s out.
#2 works fine, and will score you points with oldskool purists and php
kids, but it''s extra work compared to...
#3 get your dataset from the database and cram an extra row into it
before binding:
private void PopulateFamilyList()
{
DataSet ds = Family.List();
ds.Tables[0].Rows.InsertAt(ds.Tables[0].NewRow(), 0);
DataView dv = ds.Tables[0].DefaultView;
dv.Sort = Family.Columns.FamilyName;
selFamilyID.DataSource = dv;
selFamilyID.DataValueField = Family.Columns.FamilyID;
selFamilyID.DataTextField = Family.Columns.FamilyName;
selFamilyID.DataBind();
}
Good luck!
Jason Kester
Expat Software Consulting Services
http://www.expatsoftware.com/
---
Get your own Travel Blog, with itinerary maps and photos!
http://www.blogabond.com/
After data binding, DropDownList.Items.Inser (0, "")
"Randall Parker" <NOtechieSPAMpundit_please@future_avoidjunk_pundit .com>
wrote in message news:%2****************@tk2msftngp13.phx.gbl...
Using DropDownList to create select/option tags in HTML how to make the
first option
be a blank string?
I have fields with optional values. Currently I''m populating the
DropDownList by
querying out a list of choices from a table. But the table shouldn''t have a
blank row.
A couple of possibilities:
1) Use a UNION query. I''ve done this in MS Access with combo boxes and the
first
member of the union returns a single row. I can''t remember the SQL syntax
for
returning a single row that is not from a table though. Anyone know how?
2) Populate the DropDownList in CodeBehind without a bind of a result set.
Just add a
blank row and then do a foreach on the dataset that has the real rows and
add all them.
3) Some other approach?
Siva M wrote:After data binding, DropDownList.Items.Inser (0, "")
I''d recommend against this. DataBound controls flip out sometimes when
you modify them after binding.
Jason Kester
Expat Software Consulting Services
http://www.expatsoftware.com/
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