Question

I have two DropDownList controls in cascade (the second one is populated based on the selection made on the first one):

<asp:DropDownList ID="ddlProduct" runat="server" AppendDataBoundItems="true" 
    AutoPostBack="true" onselectedindexchanged="ddlProduct_SelectedIndexChanged">
    <asp:ListItem Value="" Selected="True"> - Product - </asp:ListItem>
</asp:DropDownList>

<asp:DropDownList ID="ddlCategory" runat="server" AutoPostBack="true" 
    OnSelectedIndexChanged="ddlCategory_SelectedIndexChanged" AppendDataBoundItems="true">
    <asp:ListItem Value="" Selected="True"> - Category - </asp:ListItem>
</asp:DropDownList>

In the ddlProduct.SelectedIndexChanged event handler I have the following code:

ddlCategory.DataSource = _productService.GetCategoryByProductId(ddlProduct.SelectedValue);
ddlCategory.DataTextField = "CategoryName";
ddlCategory.DataValueField = "CategoryId";
ddlCategory.DataBind();

The first time a user choose a Product from ddlProduct the ddlCategory is populated correctly. The following times, the Categories in ddlCategory are appended to those that were selected the first time and so on. I tried to put in ddlProduct.SelectedIndexChanged:

ddlCategory.Items.Clear();

but the method removes also the hardcoded item

<asp:ListItem Value="" Selected="True"> - Category - </asp:ListItem>

How can I just delete the appended item from ddlCategory?

Answer 1

You could set AppendDataboundItems="false" and insert the default item manually, for example in DropDownList.DataBound event:

protected void ddlCategory_DataBound(object sender, EventArgs e)
{
    if (ddlCategory.Items.Count > 0)
    {
            ddlCategory.Items.Insert(0, " - Category - ");
            ddlCategory.Items[0].Value = "";
            ddlCategory.SelectedIndex = 0;
        }
    }
}