下拉列表显示此代码的错误 [英] Dropdown list showing error with this code

问题描述

大家好，全部



这里我尝试在下拉列表中显示两列，当我从DB中检索显示错误对象参考错误的数据时！



我的代码是：

Hi, All

Here i try to show two columns in dropdownlist, when i retrieve the data from DB showing Error Object Reference error !

My Code IS:

DataTable Dtab_1 = new DataTable();
            Dtab_1 = DbCon.GetData("select ReasonCodeC +' /  '+ReasonNameC as ReasonD from reason");
            ddlresoncode.DataSource = Dtab_1;
            ddlresoncode.DataTextField = "ReasonD";
            ddlresoncode.DataBind();
            DataTable Dtab_2 = new DataTable();
            Dtab_2 = DbCon.GetData("select r.ReasonCodeC+' / '+r.ReasonNameC as reasonD from reason as r inner join holiday as h on r.ReasonCodeC=h.ReasonCodeC where h.HolidayNameC='" + strCmd + "'");
            ddlresoncode.Items.FindByText(Dtab_2.Rows[0]["reasonD"].ToString()).Selected = true; // Here i Got Error!

推荐答案

错误可能是由于FindByText返回NULL而你在使用它之前没有检查它。

在使用之前一定要检查对象的存在和有效性。



对象sel = ddlresoncode.Items.FindByText（Dtab_2.Rows [0] [reasonD]。ToString（））;

if（sel！ = null）

sel.Selected = True

else //做其他事情

return;

The error is probably caused by FindByText returning NULL and you not checking it before using it.
Always check for object existence and validity before using it.

Object sel = ddlresoncode.Items.FindByText(Dtab_2.Rows[0]["reasonD"].ToString());
if ( sel != null)
sel.Selected = True
else // do something else
return;

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