Error: SelectedValue which is invalid because it does not exist in the list of items

Question

I have a Gridview which binds to an ObjectDataSource (objStudentDetails). In edit/insert mode of the Gridview one of the fields is a DropDownList that gets it's pick list options from a lookup table. I have this DropDownList binding to another ObjectDataSource control (objStateList) which represents the lookup table. It works fine as long as the value in the objStudentDetails ObjectDataSource matches one of the values in the objStateList ObjectDataSource, at least in the case of a non empty string value anyway.

The objStateList has these values (from the stored proc that loads it - ID#6 is an empty string ''):

StateId     State
----------- -----
6             
4           AL
1           GA
3           KY
2           TN

The objStudentDetails has these values (from the stored proc that loads it):

FirstName   LastName   State
----------- ---------- -----
tone        smith      TN

Or it could have this result set (State is an empty string - ''):

FirstName   LastName   State
----------- ---------- -----
jenny       johnson     

In the first objStudentDetails resultset the state DropDownList in the EditItemTemplate shows up fine. In the second resultset, however, I get this error:

'ddlEditState' has a SelectedValue which is invalid because it does not exist in the list of items.
Parameter name: value 

I would think that since my lookup table has a value with an empty string, that the objStudentDetails value with an empty string for state would match, but something isn't working the way I am expecting it to.

Here is my EditItemTemplate code from the Gridview:

<EditItemTemplate>
  <asp:Panel ID="panEditState" runat="server">
    <asp:DropDownList ID="ddlEditState" runat="server" CssClass="GridviewDropdownlist"
      DataSourceID="objStateList" DataTextField="State" DataValueField="State"      
      SelectedValue='<%# Bind("State") %>'
      Width="50px">
</asp:DropDownList>
</asp:Panel>
</EditItemTemplate>

And the objStateList, which calls a method passing a parameter of which lookup table to query:

<asp:ObjectDataSource ID="objStateList" runat="server" SelectMethod="GetDropdownData"     TypeName="AIMLibrary.BLL.DropdownData">
<SelectParameters>
<asp:Parameter Name="itemsToGet" DefaultValue="state" />
</SelectParameters>
</asp:ObjectDataSource>

Any ideas?

Answer 1

Start by setting both DropDownLists' AppendDataBoundItems property to true. Next, add the NULL ListItem by adding the following <asp:ListItem> element to each DropDownList so that the declarative markup looks like:

<asp:DropDownList ID="Categories" runat="server"
    DataSourceID="CategoriesDataSource" DataTextField="CategoryName"
    DataValueField="CategoryID" SelectedValue='<%# Bind("CategoryID") %>'
    AppendDataBoundItems="True">
    <asp:ListItem Value="">[nothing selected]</asp:ListItem>
</asp:DropDownList>

Answer 2

I suspect there are many different scenarios that can cause this error. In my case, I had a drop down placed in a template field. The drop down was bound to its own objectdatasource, and its selectedvalue property was bound to a field from the gridview's own (separate) datasource.

Now, with my specific scenario, the problem was a race condition. The gridview's datasource was being populated and bound BEFORE the dropdowns had their turn. This also meant that the dropdowns' selectedvalues were being set BEFORE the dropdowns' items had been created through their own bindings.

I'm sure there's got to be a better solution, but I didn't have much time for research. I disconnected the gridview and the dropdowns from their datasources (meaning, removing the assignments from the designer) and opted bind programmatically. That way, I can explicitly bind the dropdowns so that their items' values will be available when the gridview itself is bound.

So far, so good. Just a few extra lines of code in the Page_Load

Answer 3

AppendDataBoundItems="True"> works but not in all cases. Making dropdownlist inside GridView is still a mystery which Microsoft has to resolve. They say development is ASP is much quicker than PHP. Well this is my third day on this small problem and still have no solution.

Answer 4

OK, since this is a common problem I guess its worth to actually post an answer: After a lot of looking around I've found two solutions - well, one patch and one real one.

1. Patching: Set the DDL setting AppendDataBoundItem=true anda add manually one element to the list (i.e. "Please Select" with null value):

   < asp:DropDownList ID="DropDownList5 runat="server" AppendDataBoundItems="True" ... > < asp:ListItem>Please Select< /asp:ListItem> < /asp:DropDownList>

This seems to work in about 80% of cases. I had a weird situation when I had to upgrade existing (and working) query used by DDL to allow another value of parameter - Query was something similar to SELECT ID, Name from EMPLOYEES where Department =@Department and originally @Department could only be equal to "Planners" and "Workshop" - after adding "Logistics" DDL mysteriously stopped working ONLY for the new value of department.

2. Proper solution: Bind the DDL during the GridView_RowDataBound event (fount thanks to This article

My parameter is taken as a text from the label (set up somewhere else)

    protected void GridView5_RowDataBound(object sender, GridViewRowEventArgs e)
    {

    //********** this  is a workaround for the annoying problem with dropdownlist in gidview without adding new item ************
    if (e.Row.RowType == DataControlRowType.DataRow && GridView5.EditIndex == e.Row.RowIndex)
    {
        DropDownList DropDownList5 = (DropDownList)e.Row.FindControl("DropDownList5");
        string query = "SELECT gkey as empID, name FROM [employees] where department=@department";
        SqlCommand command = new SqlCommand(query);
        command.Parameters.AddWithValue("@department", lblDepartment.Text);
        DropDownList5.DataSource = GetData(command);
        DropDownList5.DataTextField = "name";
        DropDownList5.DataValueField = "empID";
        DropDownList5.DataBind();
    }

And the GetData method:

   private DataTable GetData (SqlCommand cmd)
{
    string strConnString = ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString;
    using (SqlConnection con = new SqlConnection(strConnString))
    {
        using (SqlDataAdapter sda = new SqlDataAdapter())
        {
            cmd.Connection = con;
            sda.SelectCommand = cmd;
            using (DataTable dt= new DataTable())
            {
                sda.Fill(dt);
                return dt;
            }
        }
    }
}