ddl Selected Index vs Selected Value
Obviously I'm missing something...in all my debugging I find that when trying to set the selectedindex to my dropdownlist that all previous logic goes out the window! In standard VB, setting the selectedindex meant referring to it's option value. What I find now is there is a distinct index array collection not based on the listitem value.
To summarize, I have a datagrid with template column that contains a read-only textbox for it's Item Template and a dynamic dropdownlist for it's Edit Item Template. When the edit hyperlink command is clicked, I grab the text value from the textbox and call to database to get the recordid for the value which will then server as the listitems "value" along with it's original "text" value.
This is the code that I am trying to use to set the selectedindex for the dropdownlist after binding the data: (note: strValue is the value found for the 'option value' for the listitem)
CType(e.Item.FindControl("gridPageDropDown"), DropDownList).SelectedIndex = CType(e.Item.FindControl("gridPageDropDown"), DropDownList).Items.IndexOf(CType(e.Item.FindControl("gridPageDropDown"), DropDownList).Items.FindByValue(strValue))
While stepping through debug, I find that strValue is set correctly...ie: "3" but at this line of code I get the following error:
System.NullReferenceException: Object reference not set to an instance of an object
and here is the stack trace:
[NullReferenceException: Object reference not set to an instance of an object.]
CSPD.pageadmin.pagesGrid_EditCommand(Object source, DataGridCommandEventArgs e) in C:\BACKUP_WEBSITES\CSPD\UserControls\pageadmin.ascx.vb:135
System.Web.UI.WebControls.DataGrid.OnEditCommand(DataGridCommandEventArgs e) +110
System.Web.UI.WebControls.DataGrid.OnBubbleEvent(Object source, EventArgs e) +466
System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +26
System.Web.UI.WebControls.DataGridItem.OnBubbleEvent(Object source, EventArgs e) +100
System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +26
System.Web.UI.WebControls.LinkButton.OnCommand(CommandEventArgs e) +120
System.Web.UI.WebControls.LinkButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +115
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +18
System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +138
System.Web.UI.Page.ProcessRequestMain() +1263
ANY DIRECTION WOULD BE HIGHLY APPRECIATED
SCHLEYER
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schleyer
3/8/2004 10:28:07 PM
asp.net.web-forms
93655 articles. 
6 followers.
3 Replies
976 Views
I'm wondering why you wrote this the way you did:CType(e.Item.FindControlAre you working on an entry for a "Most obfusicated code" contest or something? Try breaking it down into its parts. You'll find that its a whole lot easier to understand and debug. Or do you plan on never sleeping between the time you write it and the time you have to modify it when the users come up with a change? Try doing it like this
("gridPageDropDown"), DropDownList).SelectedIndex = CType(e.Item.FindControl
("gridPageDropDown"), DropDownList).Items.IndexOf(CType(e.Item.FindControl
("gridPageDropDown"), DropDownList).Items.FindByValue(strValue))You don't even need to know the selected index in this code. If you are 100% certain that the item will always be there to be found, you could omit the "If Not Itm Is Nothing", and if you're certain there will never be an item already selected, you can omit the "clearSelection". I don't think there can be more than one opinion over which code is easier to write, understand and debug.
Dim ddl As DropDownList = CType(e.Item.FindControl("gridPageDropDown"), DropDownList)
Dim itm As ListItem = ddl.Items.FindByValue(strValue)
If Not itm Is Nothing Then ' allow for a not-found condition
ddl.ClearSelection() ' in case there was a prior selection
itm.Selected = True
End If
Sorry to pick on your code that way. But I think the way it is written is a big part of why you're having a hard time figuring out what's wrong with it.
Jim
MS MVP ASP.NET [VC++/MFC emeritus]
Old Dog Learns New Tricks
Preferred programming language: cuneiform on clay tablets
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JimRoss
3/8/2004 10:57:46 PM
Thank you for setting me straight on complexity...I knew my code was getting outta control because of that...that's why I posted...I've worked and researching so much on this that I'm was truly lost
I posted the above code, but realized that my orig logic was off...I was trying to findcontrol after all the databinding was done and there is one ddl per row in my datagrid.
Now am having another problem...hopefully minor. I inserted an onload into my asp:dropdownlist tag and placed the code in that sub...code is below
<EditItemTemplate>
<asp:DropDownList ID=gridPageDropDown runat=server datavaluefield="pageid" DataTextField="pagename" DataSource="<%#TempDataView%>" onload="<%# SetIndex(source,args)%>"></asp:DropDownList>
</EditItemTemplate>
Public Sub SetIndex()
Dim connection As New SqlConnection(connectionString)
connection.Open()
Dim strSQL As String
strSQL = "SELECT pageid FROM pages where pagename = '" & Replace(gridPageDropDownValue.ToString, "'", "''") & "'"
Dim objCmd As SqlCommand = New SqlCommand(strSQL, connection)
Dim strValue As Object = CStr(objCmd.ExecuteScalar())
Dim ddl As DropDownList = CType(pagesGrid.FindControl("gridPageDropDown"), DropDownList)
'''Dim ddl As DropDownList = gridPageDropDown
Dim itm As ListItem = ddl.Items.FindByValue(strValue)
If Not itm Is Nothing Then ' allow for a not-found condition
ddl.ClearSelection() ' in case there was a prior selection
itm.Selected = True
End If
connection.Close()
End Sub
----------------
The code doesn't error, but it still doesn't select the item. I modified your original code because I didn't have the 'e' args since this is custom function. The 'gridPageDropDown' didn't automatically inhert in my codebehind...assuming that's because the ddl is embedded withint the datagrid. I typed it in manually like:
Protected WithEvents gridPageDropDown As System.Web.UI.WebControls.DropDownList
and then tried using the commented code above, but no luck.
PLEASE FORGIVE MY FRUSTRATION AND IGNORANCE...I have learned so much in .NET and have not had such issues with anything else...
Schleyer
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schleyer
3/8/2004 11:39:17 PM
STILL UNRESOLVED
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schleyer
3/9/2004 1:10:59 AM
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