Dropdownlist回发中的选定值

Question

I have 2 dropdownlists(ddl1,ddl2) and a gridview with 2 dropdown lists(gddl1,gddl2). On SelectedIndexChanged event of ddl1 am changing SelectedIndex of gddl1 in postback.

My problem is ddl1.databind() occurs at a button's click event . So once selectedindex of ddl1 changes, the selected value losts and returns back to initial value.

I cant use !IsPostback because am binding ddl1 on button click. How can I retain ddl1 and ddl2 selected index.?

protected void btnProceed_Click(object sender, EventArgs e)
{
    if(ddlLocation.SelectedIndex > -1) {
        empDS = ws_service.GetEmpList(ddlLocation.SelectedValue, ((ddlDept.SelectedValue == "All") ? "" : ddlDept.SelectedValue), ((ddlGrade.SelectedValue == "All") ? "" : ddlGrade.SelectedValue));
        appraiserDS = ws_service.GetAppList();
        grdDetails.DataSource = empDS.Tables[ 0 ].DefaultView;
        grdDetails.DataBind();

        ddlAppraiserAll.DataSource = appraiserDS.Tables[ 0 ].DefaultView;
        ddlAppraiserAll.DataTextField = "APPRAISER_NAME";
        ddlAppraiserAll.DataValueField = "APPRAISER_ID";
        ddlAppraiserAll.DataBind();
    }
}


protected void ddlAppraiserAll_SelectedIndexChanged(object sender, EventArgs e)
{
    foreach(GridViewRow gvRow in grdDetails.Rows) {
        Control ctrl = gvRow.FindControl("ddlAppraiserId");
        DropDownList ddl = ctrl as DropDownList;
        if(ddl != null)
            ddl.SelectedIndex = ddlAppraiserAll.SelectedIndex;
    }
}

Answer 1

这里的问题是同步及其在何处以及在何处进行绑定，但是您也可以使用Request.Form直接获取值。

Request.Form[DropDownListID.UniqueID]

Answer 2

I'm not sure if i understood your problem since it's difficult to see what's ddl1 , ddl2 , gddl1 and so on and when each event is handled.

But my guess is:

• DataBind your GridView in btnProceed_Click
• Bind the two DropDownLists of the GridView only in RowDataBound

Then your "GridView-DropDownLists" are always up-to-date according to the selected value of ddl1

Answer 3

you can retain ddl1 and ddl2 selected index by storing them in viewstate as properties.

        private string ddlSelectedIndex
    {
        set { ViewState["SelectedIndex"] = value; }
        get { return ViewState["SelectedIndex"] == null ? string.Empty : ViewState["SelectedIndex"].ToString(); }
    }

The above property is in string, you can create an int property in similar way or use the same and cast index as string. Your selected index will be retained on subsequent postbacks.