VB.net中的DropDownList [英] DropDownList in VB.net

问题描述

我的页面上有一个下拉列表ctrl.

我编码为代码隐藏文件中的下拉列表设置datasoure.

我的问题是，每当页面回发时dropdownlist数据源都不存在，并且运行以下代码?

我想在页面首次加载后运行代码.

 如果 UnitName_ddl.DataSource 是 什么都没有 然后
                 Dim  dt  As   New  DataTable(" )
                dt.Columns.Add(" )
                dt.Rows.Add(" )
                dt.Rows.Add(" )
                dt.Rows.Add(" )
                UnitName_ddl.DataSource = dt
                UnitName_ddl.DataBind()
            结束 如果 

解决方案

我认为您必须在每个回发事件中重置 datasoure .

请在PostBack的外面写代码

//Write code here..
if(!IsPostback)
{
//Remove code from here..
}

如果您仍有问题，请告诉我. :)

谢谢，
Imdadhusen

如果您的控件处于活动状态，请尝试page_load事件:

If not ispostback Then

             Dim dt As New DataTable("Unit_tbl")
              dt.Columns.Add("UnitName")
              dt.Rows.Add("--Select UnitName--")
              dt.Rows.Add("KOTAK")
              dt.Rows.Add("ICICI BANK LTD")
              UnitName_ddl.DataSource = dt
              UnitName_ddl.DataBind


End If

如果禁用了viewstate，则每次页面回发时都必须加载您的值.

I have a dropdownlist ctrl in my page.

I code to set datasoure for dropdownlist in codebehide file.

My question is whenever the page is postback the dropdownlist datasource is nothing and the following code run?

I would like to run the code once page first load.

If UnitName_ddl.DataSource Is Nothing Then
                Dim dt As New DataTable("Unit_tbl")
                dt.Columns.Add("UnitName")
                dt.Rows.Add("--Select UnitName--")
                dt.Rows.Add("KOTAK")
                dt.Rows.Add("ICICI BANK LTD")
                UnitName_ddl.DataSource = dt
                UnitName_ddl.DataBind()
            End If

解决方案

Hi Usankardurai,

I think you will have to reset datasoure at every postback event.

Please write the code out side of the PostBack

//Write code here..
if(!IsPostback)
{
//Remove code from here..
}

Please do let me know, if you still have problem. :)

Thanks,
Imdadhusen

If you have viewstate active for your control try on page_load event:

If not ispostback Then

             Dim dt As New DataTable("Unit_tbl")
              dt.Columns.Add("UnitName")
              dt.Rows.Add("--Select UnitName--")
              dt.Rows.Add("KOTAK")
              dt.Rows.Add("ICICI BANK LTD")
              UnitName_ddl.DataSource = dt
              UnitName_ddl.DataBind


End If

If viewstate is disabled you have to load your values each time the page is postedback.

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