How to update the SQLDataSource of a DropDownList from code-behind

Question

I have two dropdownlists:

<td style="width: 20%;">
    <!-- TASK NAME -->
    <asp:DropDownList ID="ddlTaskName" DataSourceID="dsPopulateTaskName" AutoPostBack="true" DataValueField="Task Name" runat="server" AppendDataBoundItems="true" OnSelectedIndexChanged="ddlTaskName_onSelectIndexChanged">
        <asp:ListItem Text="All" Value="%"></asp:ListItem>
    </asp:DropDownList>
    <asp:SqlDataSource ID="dsPopulateTaskName" runat="server" ConnectionString="<%$ ConnectionStrings:gc %>" SelectCommand=""></asp:SqlDataSource>
</td>
<td style="width: 20%;">
    <!-- SERVICE -->
    <asp:DropDownList ID="ddlService" DataSourceID="dsPopulateService" AutoPostBack="true" DataValueField="Service" runat="server" AppendDataBoundItems="true" OnSelectedIndexChanged="ddlService_onSelectIndexChanged">
        <asp:ListItem Text="All" Value="%"></asp:ListItem>
    </asp:DropDownList>
    <asp:SqlDataSource ID="dsPopulateService" runat="server" ConnectionString="<%$ ConnectionStrings:gc %>" SelectCommand=""></asp:SqlDataSource>
</td>

code-behind on Page_Load:

strForDropDownList = @" FROM [Db].[dbo].[table1] WHERE [stat] = 'A'";
string pol = " AND ";
if (ddlTaskName.SelectedIndex == 0)
{
    pol += " ([tcol] LIKE '%' OR [tcol] IS NULL) AND ";
}
else
{
    pol += " [tcol] = '" + ddlTaskName.SelectedValue.TrimEnd() + "' AND ";
}
if (ddlService.SelectedIndex == 0)
{
    pol += " (scol LIKE '%' OR scol IS NULL) AND ";
}
else
{
    pol += " scol = '" + ddlService.SelectedValue.TrimEnd() + "' AND ";
}
strWhere = pol;
dsPopulateTaskName.SelectCommand = @"SELECT DISTINCT [tcol] 'Task Name'" + strForDropDownList + strWhere;
dsPopulateService.SelectCommand = @"SELECT DISTINCT scol 'Service'" + strForDropDownList + strWhere;

When the page loads, everything starts with % and populates the dropdownlists correctly. If I select an option from the ddlService dropdownlist, the dsPopulateTaskName.SelectCommand displays the correct query to repopulate the ddlTaskName dropdownlist but it doesn't update it.

Please help me resolve it.

TylerH · Accepted Answer · 2025-09-30 19:24:06Z

1

You should call ddlService.DataBind() and ddlTaskName.DataBind() after setting the SelectCommand, like below:

dsPopulateTaskName.SelectCommand = 
@"SELECT DISTINCT [tcol] 'Task Name'" + strForDropDownList + strWhere;
ddlService.DataBind();

dsPopulateService.SelectCommand = 
@"SELECT DISTINCT scol 'Service'" + strForDropDownList + strWhere;
ddlTaskName.DataBind();

edited Sep 30 at 19:24

TylerH

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answered Mar 13, 2015 at 14:54

Nima Derakhshanjan

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3 Comments

SearchForKnowledge Over a year ago

Thank you. I have it like this: ddlTaskName.Items.Clear();ddlTaskName.DataBind(); and it works fine except I lose the All which should always exist.

Nima Derakhshanjan Over a year ago

you don't have to use that line : ddlTaskName.Items.Clear(); it will refresh on databinding

Nima Derakhshanjan Over a year ago

well,if suppose to update the dropdownlist in SelectIndexChanged please call ddlTaskName.DataBind(); in SelectIndexChanged after setting SelectCommand

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