Question

我在同一个aspx页面上有两个下拉列表控件

<asp:DropDownList ID="ddlM" runat="server" Width="123px" AutoPostBack="True" OnSelectedIndexChanged="ddlM_SelectedIndexChanged">
</asp:DropDownList>

<asp:DropDownList ID="ddlC" runat="server" Width="123px" AutoPostBack="True" OnSelectedIndexChanged="ddlC_SelectedIndexChanged">
</asp:DropDownList>

OnSelectedIndexChanged的C＃代码如下：

protected void ddlC_SelectedIndexChanged(object sender, EventArgs e)
{
   ddlM.SelectedIndex = 0;
   ViewState["ddlC"] = true;
   ViewState["ddlM"] = false;                 
   BindPGrid();            
}

protected void ddlM_SelectedIndexChanged(object sender, EventArgs e)
{
   ddlC.SelectedIndex = 0;                
   ViewState["ddlC"] = false;
   ViewState["ddlM"] = true; 
   BindPGrid();
}

使用某些服务器端代码填充数据库记录项。现在，OnSelectedIndexChanged事件“ddlM”我想选择“ddlC”的第一个索引但是没有触发事件ddlC_SelectedIndexChanged。对于“ddlC”和“ddlC”的OnSelectedIndexChanged事件一样，我想选择“ddlM”的第一个索引但是没有触发事件ddlM_SelectedIndexChanged。对不起它发射事件。我怎么办呢？

由于

Answer 1

或者，您可以从控件中删除并重新添加SelectedIndexChanged事件处理程序

 ddlM.SelectedIndexChanged -= ddlM_SelectedIndexChanged;

 ddlM.SelectedIndex = 0;
 ViewState["ddlC"] = false;
 ViewState["ddlM"] = true; 
 BindPGrid();

 ddlM.SelectedIndexChanged += ddlM_SelectedIndexChanged;

然后你不必乱用全球旗帜

Answer 2

在这种情况下，我们会创建一个全局bool标记，并在更改true之前将其值设置为SelectedIndexChanged。在其他Control的SelectedIndexChanged中检查其值是否为真。如果是真的，我们会在活动之外返回。并在外面再次更改标志值。确保始终将标志值更改回false，否则如果该事件由同一控件生成，则永远不会触发。

boool flag = false;

protected void ddlC_SelectedIndexChanged(object sender, EventArgs e)
{
   flag = true;
   ddlM.SelectedIndex = 0;
   flag = false;
   ViewState["ddlC"] = true;
   ViewState["ddlM"] = false;                 
   BindPGrid();            
}

protected void ddlM_SelectedIndexChanged(object sender, EventArgs e)
{
   if(flag)
       return;

   ddlC.SelectedIndex = 0;                
   ViewState["ddlC"] = false;
   ViewState["ddlM"] = true; 
   BindPGrid();
}

或者你可以删除像

这样的事件处理程序

protected void ddlC_SelectedIndexChanged(object sender, EventArgs e)
{
   ddlM.SelectedIndexChanged -= ddlM_SelectedIndexChanged;
   ddlM.SelectedIndex = 0;
   ddlM.SelectedIndexChanged += ddlM_SelectedIndexChanged;
   ViewState["ddlC"] = true;
   ViewState["ddlM"] = false;                 
   BindPGrid();            
}

asp.net c＃在从服务器端代码更改索引时阻止触发selectedindexchanged事件

2 个答案: