Cannot have multiple items selected in a DropDownList
2010-04-24 12:36
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有时,当我们试图指定一个ASP.NET Dropdownlist选中的项目时遇到这样的报错”Cannot have multiple items selected in a DropDownList.”
使用下面这些代码有可能出现这个报错:
DropDownList1.Items.FindByValue(”3″).Selected = true;
或者
DropDownList1.Items.FindByText(”Sports”).Selected = true;
如果这样写代码却不会出现这种报错:
DropDownList1.SelectedIndex = 3;
或者
DropDownList1.SelectedItem.Value = “3″; (Wrong way of implementation. But people use this)
正确代码示范如下:
DropDownList1.ClearSelection();
DropDownList1.Items.FindByValue(”3″).Selected = true;
或者
DropDownList1.ClearSelection();
DropDownList1.Items.FindByText(”Sports”).Selected = true;
转自:http://www.lynncn.cn/?p=296
使用下面这些代码有可能出现这个报错:
DropDownList1.Items.FindByValue(”3″).Selected = true;
或者
DropDownList1.Items.FindByText(”Sports”).Selected = true;
如果这样写代码却不会出现这种报错:
DropDownList1.SelectedIndex = 3;
或者
DropDownList1.SelectedItem.Value = “3″; (Wrong way of implementation. But people use this)
解决的方法
在DropDownList1.Items.FindByValue(”3″).Selected = true;的前面加上一句DropDownList1.ClearSelection();正确代码示范如下:
DropDownList1.ClearSelection();
DropDownList1.Items.FindByValue(”3″).Selected = true;
或者
DropDownList1.ClearSelection();
DropDownList1.Items.FindByText(”Sports”).Selected = true;
为什么
原因很简单,当你使用 DropDownList1.Items.FindByText(”Sports”).Selected = true;这种形式指定某个item的Selected为true时,之前已经选择的item的Selected值仍然为true,而DropDownList是不允许多个值被同时选定的,所以会报错。转自:http://www.lynncn.cn/?p=296
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