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how do you bind dropdownlist with in edit mode with item is not in the list

Posted on 2009-05-07
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Last Modified: 2013-11-08
expert: I have a asp .net C# web INSERT and EDIT Mode FormView with a dropdownlist with "make a selection" as one of the choices. The DDL is loaded from a db table list which does not include "make a selection". When user does not make a selection a NULL is inserted into the db record . However when I bring the record up and click the edit link I get error "SelectedValue which is invalid because it does not exist in the list of items". I am not sure how to fix this issue?  My code is below:
<asp:DropDownList ID="MYDdl" runat="server" AppendDataBoundItems="True"
                                        DataSourceID="MYTypeDataSource" DataTextField="car_type"    
                                        DataValueField="car_type"
                                        SelectedValue='<%# Bind("car_type") %>' Width="200px">
                                        <asp:ListItem Value="-1">--make a selection --</asp:ListItem>
                      </asp:DropDownList>
 
                  // C# code behind
                   if (MYDdl.SelectedValue == "-1")
                    {
                        e.Values["car_type"] = null;
                      
                    }

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Question by:tcmmaxt
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Expert Comment

by:mohan_sekar
ID: 24329154
What do you want to do -> handle the case where you get a null value from the database? Or, prevent inserting a null value in to the database?
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by:tcmmaxt
ID: 24329243
expert: What do you want to do -> handle the case where you get a null value from the database
Yes -->handle the case where you get a null value from the database
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mohan_sekar earned 500 total points
ID: 24329305
Ok, you got to do two things.
Set 'AppendDataBoundItems' to True for the Dropdown list. In Page_Load, add the following line
dropdownlist.items.add("Please make a selection");

Step 2: when you get a null value from the database, select the 1st item
dropdownlist.selectedindex = 0;
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