假设你的 DetailsView 有 DataSourceID 属性设置为SqlDataSource1，您不需要处理 ItemInserting 代码隐藏中的事件。 <％＃Bind（...）％> 语句会自动将所选值传递给数据源控件上的参数。

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编辑：尝试将填充列表的代码移动到 Init 事件中控制。这将为您提供与声明标记中的项目相同的结果：

Assuming your DetailsView has its DataSourceID property set to "SqlDataSource1", you don't need to handle the ItemInserting event in the code-behind. The <%# Bind("...") %> statements will automatically pass the selected values to the parameters on the data-source control.

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Try moving the code which populates the lists to the Init event of the control. This will give you the same result as declaring the items in the markup:

<InsertItemTemplate>
    <asp:DropDownList ID="DropDownListDay" runat="server" 
        Width="50px" SelectedValue='<%# Bind("BirthDateDay") %>' 
        OnInit="DayList_Init"
    />
    <asp:DropDownList ID="DropDownListMonth" runat="server" 
        Width="50px" SelectedValue='<%# Bind("BirthDateMonth") %>'
        OnInit="MonthList_Init"
    />
    <asp:DropDownList ID="DropDownListYear" runat="server" 
        Width="70px" SelectedValue='<%# Bind("BirthDateYear") %>'
        OnInit="YearList_Init"
    />
</InsertItemTemplate>

protected void DayList_Init(object sender, EventArgs e)
{
    var list = (DropDownList)sender;
    for (int i = 1; i < 32; i++)
    {
        list.Items.Add(new ListItem(i.ToString());
    }
}

protected void MonthList_Init(object sender, EventArgs e)
{
    var list = (DropDownList)sender;
    for (int i = 1; i < 13; i++)
    {
        list.Items.Add(new ListItem(i.ToString());
    }
}

protected void YearList_Init(object sender, EventArgs e)
{
    var list = (DropDownList)sender;
    for (int i = 1300; i < 1396; i++)
    {
        list.Items.Add(new ListItem(i.ToString());
    }
}