ASP如何在详细信息视图中绑定下拉列表的选定值

Question

I have a dropdownlist in a detailsview control. The data source is a SQL table with a dayofthemonth column.

<asp:TemplateField HeaderText="Day of Month: ">
            <EditItemTemplate>
                <asp:DropDownList ID="ddlDoM" runat="server" > 
                </asp:DropDownList>
            </EditItemTemplate>
            <InsertItemTemplate>
                <asp:TextBox ID="TextBox6" runat="server" Text='<%# Bind("dayofthemonth") %>'></asp:TextBox>
            </InsertItemTemplate>
            <ItemTemplate>
                <asp:Label ID="Label7" runat="server" Text='<%# Bind("dayofthemonth") %>'></asp:Label>
            </ItemTemplate>
            <HeaderStyle Font-Bold="True" />
</asp:TemplateField>

I have populated the dropdownlist with numbers 1 - 31 in the DataBound event.

protected void DataView1_DataBound(object sender, EventArgs e)
{
    DropDownList ddlDoM = (DropDownList)Page.FindControl("ctl00$formPlaceHolder$DataView1$ddlDoM");
    if (DataView1.CurrentMode == DetailsViewMode.Edit)
    {
        for (int i = 1; i < 32; i++)
        {
            ListItem item = ListItem.FromString(i.ToString());
            ddlDoM.Items.Add(item);
        }
    }
        DataRowView drv = DataView1.DataItem as DataRowView;
        ddlDoM.SelectedIndex = ddlDoM.Items.IndexOf(ddlDoM.Items.FindByValue(drv["dayofthemonth"].ToString()));
    }
}

In the final line here, I set the selected value of the dropdownlist to the current data source value.

ddlDoM.SelectedIndex = ddlDoM.Items.IndexOf(ddlDoM.Items.FindByValue(drv["dayofthemonth"].ToString()));

How can I bind the dropdownlist to update the value in the datasource when changed? I have tried setting the selected value property to <%# Bind("dayofthemonth") %> , but I receive an OutOfRangeException. I'm assuming the list hasn't populated yet in switching to Edit Mode.

Any thoughts on this? Let me know if you need more code.

Answer 1

Try adding a ControlParameter to your UpdateParameters in your datasource, and ensure your dropdown list is set to AutoPostBack if appropriate. You might also consider populating the dropdownlist in an earlier event (eg Page_Init ) and leave setting its default value until the DataBound event you already have.

<asp:SqlDataSource ... UpdateCommand=""....>
    <UpdateParameters>
        <asp:ControlParameter ControlID="ddlDoM" Name="dayofthemonth" PropertyName="SelectedValue" Type="Int32" />
    </UpdateParameters>
</asp:SqlDataSource>

Also, if it's still causing problems, a safe (but verbose) option is to add the ListItems directly to the dropdownlist control, because they seem to be static values:

<asp:DropDownList ID="ddlDoM" runat="server" AutoPostBack="true">
    <asp:ListItem Value="1" />
    <asp:ListItem Value="2" />
    <asp:ListItem Value="3" />
    etc...
</asp:DropDownList>