DropDownList 怎么绑定数据

有两种方法：一种是用dual表查空值，然后绑定。另一种是先动态绑定数据后，然后插入一列默认项。

eg1:

string selectQuery = "select null extattrid,null extattrname from dual union all select extattrid,extattrname from VExtAttrDetail where extattrsn in (22)"

DataSet ds=dboperReq.GetDSet(selectQuery)

ddlTrantype.DataTextField = "extattrname"

ddlTrantype.DataValueField="extattrid"

ddlTrantype.DataSource=ds.Tables[0].DefaultView

ddlTrantype.DataBind()

eg2:

string selectQuery = "select extattrid,extattrname from VExtAttrDetail where extattrsn in (22)"

DataSet ds=dboperReq.GetDSet(selectQuery)

ddlTrantype.DataTextField = "extattrname"

ddlTrantype.DataValueField="extattrid"

ddlTrantype.DataSource=ds.Tables[0].DefaultView

ddlTrantype.DataBind()

ddlTrantype.Items.Insert(0,new ListItem(" "," "))//或者ListItem it = new ListItem("请选择", "0")

//mydroplist.Items.Insert(0,it)或者 ListItem lt = new ListItem()

//lt.Text = "请选择"

//lt.Value = "00"

//lt.Selected = true

//ddp.Items.Add(lt)

先把两个属性设好：

DropDownList1.DataTextField

=

"name"

//下拉框显示的数据

DropDownList1.DataValueField

=

"userid"//实际的值

然后再把数据源绑定在DropDownList1上。

有先后之分：先绑定ddl_Semester，然后在ddl_Semester的SelectedIndexChanged触发事件里再绑定ddl_Course。ddl_Semester的autoPostbank设置为true（允许自动会发）这才是最重要的。

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