Question

ASP.NET Formview control dropdownlist SelectedIndexChanged problem

Asked by: DeMyu

I have problems getting the Formview control with two dependent dropdownlists to work in Edit Mode. I have say dropdownlist A and dropdownlist B where Dropdownlist B is dependent on dropdownlist A.

My goal is such that when a user clicks the edit button in the Formview the selectedvalues of dropdownlist A and dropdownlist B should be the values obtained from the database.

Here is the error message that I am receiving from the web server when I click edit to put the formview into edit mode.

Databinding methods such as Eval(), XPath(), and Bind() can only be used in the context of a databound control.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.InvalidOperationException: Databinding methods such as Eval(), XPath(), and Bind() can only be used in the context of a databound control.

The error disappears when I remove SelectedValue='<%# Bind("appID") %>' from

<asp:DropDownList ID="dropApplication" runat="server" DataTextField="appName" DataValueField="appID" SelectedValue='<%# Bind("appID") %>' />

<asp:FormView ID="FormView1" runat="server" DataKeyNames="romID">
							<EditItemTemplate>
								<table class="tblborder">
 <tr>
										<td class="formlabel"><LABEL class="reqlabel" for="dropComponent">Component:</LABEL><span class="form-required">*</span></td>
										<td align="left">	
									<asp:DropDownList ID="dropComponent" runat="server" DataSourceID="SqlDataSource01" DataTextField="orgName" DataValueField="orgID" AppendDataBoundItems="true" AutoPostBack="True" SelectedValue='<%# Bind("orgID") %>' OnSelectedIndexChanged="dropComponent_SelectedIndexChanged">
                                    <asp:ListItem Value="">
                                            -- Choose a component --
                                        </asp:ListItem>
		                           </asp:DropDownList>
		                           </td>
		                           <td><asp:RequiredFieldValidator runat="server" Display="Dynamic" ControlToValidate="dropComponent" ErrorMessage="<img src='images/common/required_trans.gif' align='absmiddle'>" />
									</td>
									</tr>
									<tr>
										<td class="formlabel"><LABEL class="reqlabel" for="dropApplication">Application:</LABEL><span class="form-required">*</span></td>
										<td align="left">	
									<asp:DropDownList ID="dropApplication" runat="server" DataTextField="appName" DataValueField="appID" SelectedValue='<%# Bind("appID") %>' />
                                    
		                           </td>
		                           <td><asp:RequiredFieldValidator runat="server" Display="Dynamic" ControlToValidate="dropApplication" ErrorMessage="<img src='images/common/required_trans.gif' align='absmiddle'>" />
									</td>
									</tr>
</table>
							</EditItemTemplate>	
 
 
----- codebehind
 
Sub dropComponent_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
 
        FormView1.ChangeMode(FormViewMode.Edit)
 
        Dim dropApplication As DropDownList = CType(FormView1.FindControl("dropApplication"), DropDownList)
        Dim dropComponent As DropDownList = CType(FormView1.FindControl("dropComponent"), DropDownList)
 
        dropApplication.Items.Clear()
 
        Dim objConn As SqlConnection = New SqlConnection(ConfigurationManager.ConnectionStrings("APPdbConnectString").ConnectionString)
 
        Dim cmdSQL As New SqlCommand("dbo.P_applications_show_active", objConn)
 
        cmdSQL.CommandType = CommandType.StoredProcedure
        cmdSQL.Parameters.Add(New SqlParameter("@orgID", SqlDbType.INT, 4)).Value = dropComponent.SelectedItem.Value
 
        Dim sqlDR As SqlDataReader
 
        Try
            objConn.Open()
 
            sqlDR = cmdSQL.ExecuteReader(CommandBehavior.CloseConnection)
 
            dropApplication.DataSource = sqlDR
            dropApplication.DataBind()
        Catch myException As Exception
            Message.InnerHtml = "<tr><th height=""25"" class=""thmsg"" colspan=""3"" nowrap=""nowrap"">" & myException.ToString() & "</th></tr>"
 
        Finally
            If Not sqlDR Is Nothing Then
                sqlDR.Close()
            End If
            dropApplication.Items.Insert(0, New ListItem("-- Choose an application --", ""))
            dropApplication.SelectedIndex = 0
        End Try
 
    End Sub

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Asked On: 2009-09-11 at 10:19:20ID24725257
Tags: ASP.NET
,; VB
,; Formview
Topic: Programming for ASP.NET
Participating Experts: 1
Points: 500
Comments: 13

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Answers

by: carlnorrbomPosted on 2009-09-11 at 23:23:55ID: 25315416

Hi,

Are you sure any items are returned for AppID? This error most likely occurs because of two reasons:

1) There are no values bound to the control
2) A value collection has been bound to the control but the value for AppID is null and null is not one of the values that has been bound to the control.

/Carl.

by: DeMyuPosted on 2009-09-12 at 15:47:10ID: 25318233

Carl,

Yes there is a value returned for AppID.

You are correct in your observation, the problem occurs because I am passing a selecteditem value to the control dropApplication when there are no values bound to the control - the Subroutine dropComponent_SelectedIndexChanged has not been activated. How can I prepopulate dropApplication with only the records that are related to the dropComponent.SelectedItem.Value (OrgID)? Remember the problem is in the edit mode of the formview.

Thank you.

DeMuy

by: DeMyuPosted on 2009-09-13 at 07:42:43ID: 25320364

I have modified my code as suggested by the author of the link http://www.webswapp.com/categories/ASPNET2/CascadingLists/vbFormView.aspx

however, I now have the error message: Could not find control 'dropApplication' in ControlParameter 'orgID'. and

the data in the dropdownlist dropApplication is not filtered based on the orgID. Any suggestion? My current code snippet is below.


<tr>
										<td class="formlabel"><LABEL class="reqlabel" for="dropComponent">Component:</LABEL><span class="form-required">*</span></td>
										<td align="left">	
									<asp:DropDownList ID="dropComponent" runat="server" DataSourceID="SqlDataSource01" DataTextField="orgName" DataValueField="orgID" AppendDataBoundItems="true" autopostback="true" SelectedValue='<%# Bind("orgID") %>' >
                                    <asp:ListItem Value="">
                                            -- Choose a component --
                                        </asp:ListItem>
		                           </asp:DropDownList>
		                           </td>
		                           <td><asp:RequiredFieldValidator runat="server" Display="Dynamic" ControlToValidate="dropComponent" ErrorMessage="<img src='images/common/required_trans.gif' align='absmiddle'>" />
									</td>
									</tr>
									<tr>
										<td class="formlabel"><LABEL class="reqlabel" for="dropApplication">Application:</LABEL><span class="form-required">*</span></td>
										<td align="left">										
											
									<asp:DropDownList ID="dropApplication" runat="server"  DataSourceID="AppSqlDS"   DataTextField="appName" DataValueField="appID" AppendDataBoundItems="true" OnDataBound="dropApplication_DataBound" >
									<asp:ListItem Value="">
                                            -- Choose an Application --
                                        </asp:ListItem>
		                           </asp:DropDownList>		                           		                           
		                           <asp:SqlDataSource ID="AppSqlDS" runat="server" ConnectionString="<%$ ConnectionStrings:APPdbConnectString %>"
                                        SelectCommand="SELECT [appID], [appName] FROM [dbo].[applications]  WHERE ([orgID] = @orgID)">
                                       <SelectParameters>                               
                                       <asp:ControlParameter ControlID="dropApplication" Name="orgID" PropertyName="SelectedValue" Type="Int32" />
                                                                      
                                       </SelectParameters>
                                   </asp:SqlDataSource>
 
------- code behind
 
 Protected Sub dropApplication_DataBound(ByVal sender As Object, ByVal e As EventArgs)
        Dim ddl As DropDownList = DirectCast(sender, DropDownList)
        'add an empty item on top of the list 
        'AddEmptyItem(ddl)
        Dim frmV As FormView = DirectCast(ddl.NamingContainer, FormView)
        If frmV.DataItem IsNot Nothing Then
            'Pull the application's value from the databound item. 
            Dim strAppID As String = DirectCast(frmV.DataItem, DataRowView)("appID").ToString()
 
            ddl.ClearSelection()
             
            Dim li As ListItem = ddl.Items.FindByValue(strAppID)
            If li IsNot Nothing Then
                li.Selected = True
            End If
        End If
       
    End Sub

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by: carlnorrbomPosted on 2009-09-13 at 09:48:57ID: 25320897

Hi,

It's probably because the dropdown is nested inside your formview, try changing the control parameter declaration to:

<asp:ControlParameter ControlID="FormView1$dropApplication" Name="orgID" PropertyName="SelectedValue" Type="Int32" />

If that doesn't fly, declare a public property in code behind and set it's value to dropApplication.ClientID.ToString() for instance in the FormView's databound event and use that in the declaration of the control parameter, i.e. ControlID="<%= ControlId %>"

/Carl.

by: DeMyuPosted on 2009-09-13 at 15:04:42ID: 25321967

Option 1 resulted in the following error messages:

Could not find control 'Formview1$dropApplication' in ControlParameter 'orgID'.

I am not sure of how to implement Option 2.

Thank you.

DeMuy

by: carlnorrbomPosted on 2009-09-14 at 00:20:36ID: 25323352

Hi,

Hmm, strange.. Option 1 usually works with nested controls. Also, I just noticed you have it wrong, the control parameter should point to dropComponent, not dropApplication -> dropApplication is the dropdown you want to populate based on the selected value of dropComponent, right?

<asp:ControlParameter ControlID="FormView1$dropComponent" Name="orgID" PropertyName="SelectedValue" Type="Int32" />

I'll get back to you with an implementation of the public property.

/Carl.

by: carlnorrbomPosted on 2009-09-14 at 01:42:11ID: 25323640

Hi,

I reviewed an old project of mine and found an even simpler solution:

Protected Sub FormView1_DataBound(ByVal sender As Object, ByVal e As System.EventArgs) Handles FormView1.DataBound
If CType(sender, FormView).CurrentMode = FormViewMode.Insert Then
Dim dropComponent As DropDownList = CType(FormView1.FindControl("dropComponent"), DropDownList)
Dim AppSqlDS As SqlDataSource = CType(FormView1.FindControl("AppSqlDS"), SqlDataSource)
AppSqlDS.SelectParameters.RemoveAt(0)
AppSqlDS.SelectParameters.Add("orgID", dropComponent .SelectedValue.ToString())
End If
End Sub

It simply checks at runtime whether the formview is in insert mode, if it is, it removes the first parameter in the collection (in this case we only have one) and replaces it with the correct dropdown. Should do the trick.

/Carl.

by: DeMyuPosted on 2009-09-14 at 08:24:29ID: 25326411

I have made the update that you've recommended above in the application. It filters the data in dropApplication based on the selectedvalue of dropComponent, however, the application is still handicapped by the following problems:

1. Error message "Could not find control 'Formview1$dropComponent' in ControlParameter 'orgID'." when I click either the cancel or update button.

2. When another value is selected from the dropComponent it fails to filter the data in the dropApplication and displays all the records in dropApplication.

</tr>
								    <tr>
										<td class="formlabel"><LABEL class="reqlabel" for="dropComponent">Component:</LABEL><span class="form-required">*</span></td>
										<td align="left">	
									<asp:DropDownList ID="dropComponent" runat="server" DataSourceID="SqlDataSource01" DataTextField="orgName" DataValueField="orgID" AppendDataBoundItems="true" autopostback="true" SelectedValue='<%# Bind("orgID") %>' >
                                    <asp:ListItem Value="">
                                            -- Choose a component --
                                        </asp:ListItem>
		                           </asp:DropDownList>
		                           </td>
		                           <td><asp:RequiredFieldValidator runat="server" Display="Dynamic" ControlToValidate="dropComponent" ErrorMessage="<img src='images/common/required_trans.gif' align='absmiddle'>" />
									</td>
									</tr>
									<tr>
										<td class="formlabel"><LABEL class="reqlabel" for="dropApplication">Application:</LABEL><span class="form-required">*</span></td>
										<td align="left">										
											
									<asp:DropDownList ID="dropApplication" runat="server"  DataSourceID="AppSqlDS"   DataTextField="appName" DataValueField="appID" AppendDataBoundItems="true" OnDataBound="dropApplication_DataBound" >
									<asp:ListItem Value="">
                                            -- Choose an Application --
                                        </asp:ListItem>
		                           </asp:DropDownList>		                           		                           
		                           <asp:SqlDataSource ID="AppSqlDS" runat="server" ConnectionString="<%$ ConnectionStrings:APPdbConnectString %>"
                                        SelectCommand="SELECT [appID], [appName] FROM [dbo].[applications] WHERE ([orgID] = @orgID)">
                                       <SelectParameters>                               
                                       <asp:ControlParameter ControlID="Formview1$dropComponent" Name="orgID" PropertyName="SelectedValue" Type="Int32" />                                                                      
                                       </SelectParameters>
                                   </asp:SqlDataSource>	                          
                                    
		                           </td>
		                           <td><asp:RequiredFieldValidator runat="server" Display="Dynamic" ControlToValidate="dropApplication" ErrorMessage="<img src='images/common/required_trans.gif' align='absmiddle'>" />
									</td>
									</tr>
 
 
---- Code Behind
 
Protected Sub dropApplication_DataBound(ByVal sender As Object, ByVal e As EventArgs)
        Dim ddl As DropDownList = DirectCast(sender, DropDownList)
        'add an empty item on top of the list 
        'AddEmptyItem(ddl)
        Dim frmV As FormView = DirectCast(ddl.NamingContainer, FormView)
        If frmV.DataItem IsNot Nothing Then
            'Pull the application's value from the databound item. 
            Dim strAppID As String = DirectCast(frmV.DataItem, DataRowView)("appID").ToString()
 
            ddl.ClearSelection()
             
            Dim li As ListItem = ddl.Items.FindByValue(strAppID)
            If li IsNot Nothing Then
                li.Selected = True
            End If
        End If
       
    End Sub
 
    Protected Sub FormView1_DataBound(ByVal sender As Object, ByVal e As System.EventArgs) Handles FormView1.DataBound
        If CType(sender, FormView).CurrentMode = FormViewMode.insert Then
            Dim dropComponent As DropDownList = CType(FormView1.FindControl("dropComponent"), DropDownList)
            Dim AppSqlDS As SqlDataSource = CType(FormView1.FindControl("AppSqlDS"), SqlDataSource)
            AppSqlDS.SelectParameters.RemoveAt(0)
            AppSqlDS.SelectParameters.Add("orgID", dropComponent.SelectedValue.ToString())
        End If
    End Sub

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by: carlnorrbomPosted on 2009-09-14 at 10:19:05ID: 25327454

Hi,

First of all, you don't need to declare a control parameter if you use the code behind. Secondly, the code behind is checking what current state the formview is in and assigns the parameter if it's in insert mode. If you want this function to work regardless of which state the formview is in, simply remove:

If CType(sender, FormView).CurrentMode = FormViewMode.insert Then
...
End If

Or alternatively, change the first line to:

If CType(sender, FormView).CurrentMode = FormViewMode.insert Or CType(sender, FormView).CurrentMode = FormViewMode.Edit Then

You need to make sure to only check for the dropdown in the modes where it is present, otherwise the code will break! Also change the select parameter to a regular parameter or remove it all together.

/Carl.

by: DeMyuPosted on 2009-09-14 at 11:04:36ID: 25327809

I have again made changes to the code as suggested and seen some improvements in the application, however, one feature that is still pending is the ability to change the records in the dropdownlist dropApplication based on the selected value of dropComponent. That is the reason behind the SelectCommand="SELECT [appID], [appName] FROM [dbo].[applications] WHERE ([orgID] = @orgID)" in the SQLdatasource. Am I missing something here?

Thanks

 <tr>
										<td class="formlabel"><LABEL class="reqlabel" for="dropComponent">Component:</LABEL><span class="form-required">*</span></td>
										<td align="left">	
									<asp:DropDownList ID="dropComponent" runat="server" DataSourceID="SqlDataSource01" DataTextField="orgName" DataValueField="orgID" AppendDataBoundItems="true" autopostback="true" SelectedValue='<%# Bind("orgID") %>' >
                                    <asp:ListItem Value="">
                                            -- Choose a component --
                                        </asp:ListItem>
		                           </asp:DropDownList>
		                           </td>
		                           <td><asp:RequiredFieldValidator runat="server" Display="Dynamic" ControlToValidate="dropComponent" ErrorMessage="<img src='images/common/required_trans.gif' align='absmiddle'>" />
									</td>
									</tr>
									<tr>
										<td class="formlabel"><LABEL class="reqlabel" for="dropApplication">Application:</LABEL><span class="form-required">*</span></td>
										<td align="left">										
											
									<asp:DropDownList ID="dropApplication" runat="server"  DataSourceID="AppSqlDS"   DataTextField="appName" DataValueField="appID" AppendDataBoundItems="true" OnDataBound="dropApplication_DataBound" >
									<asp:ListItem Value="">
                                            -- Choose an Application --
                                        </asp:ListItem>
		                           </asp:DropDownList>		                           		                           
		                           <asp:SqlDataSource ID="AppSqlDS" runat="server" ConnectionString="<%$ ConnectionStrings:APPdbConnectString %>"
                                        SelectCommand="SELECT [appID], [appName] FROM [dbo].[applications] WHERE ([orgID] = @orgID)">
                                      <SelectParameters> 
                                      <asp:Parameter Name="orgID" Type="int32" />                           
                                                                                                             
                                       </SelectParameters>
                                   </asp:SqlDataSource>	
		                           </td>
		                           <td><asp:RequiredFieldValidator runat="server" Display="Dynamic" ControlToValidate="dropApplication" ErrorMessage="<img src='images/common/required_trans.gif' align='absmiddle'>" />
									</td>
									</tr>
 
 
--- code behind
 
Protected Sub FormView1_DataBound(ByVal sender As Object, ByVal e As System.EventArgs) Handles FormView1.DataBound
 
        If CType(sender, FormView).CurrentMode = FormViewMode.insert Or CType(sender, FormView).CurrentMode = FormViewMode.Edit Then
 
            Dim dropComponent As DropDownList = CType(FormView1.FindControl("dropComponent"), DropDownList)
            Dim AppSqlDS As SqlDataSource = CType(FormView1.FindControl("AppSqlDS"), SqlDataSource)
            AppSqlDS.SelectParameters.RemoveAt(0)
            AppSqlDS.SelectParameters.Add("orgID", dropComponent.SelectedValue.ToString())
        End If
    End Sub
 
Protected Sub dropApplication_DataBound(ByVal sender As Object, ByVal e As EventArgs)
        Dim ddl As DropDownList = DirectCast(sender, DropDownList)
        'add an empty item on top of the list 
        'AddEmptyItem(ddl)
        Dim frmV As FormView = DirectCast(ddl.NamingContainer, FormView)
        If frmV.DataItem IsNot Nothing Then
            'Pull the application's value from the databound item. 
            Dim strAppID As String = DirectCast(frmV.DataItem, DataRowView)("appID").ToString()
 
            ddl.ClearSelection()
             
            Dim li As ListItem = ddl.Items.FindByValue(strAppID)
            If li IsNot Nothing Then
                li.Selected = True
            End If
        End If
       
    End Sub

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by: carlnorrbomPosted on 2009-09-14 at 12:27:02ID: 25328473

Hi,

Try the following:

1. Remove all the code in the FormView1_DataBound() method
2. Add the following method:

Protected Sub dropComponent_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs)
Dim dropApplication As DropDownList = CType(FormView1.FindControl("dropApplication"), DropDownList)
Dim AppSqlDS As SqlDataSource = CType(FormView1.FindControl("AppSqlDS"), SqlDataSource)
dropApplication.Items.Clear()
dropMake.Items.Add(New ListItem("-- Choose an application --", ""))
AppSqlDS.SelectParameters.Clear()
AppSqlDS.SelectParameters.Add("orglID", CType(sender, DropDownList).SelectedValue)
End Sub

3. Change your markup for the dropComponent to:

<asp:DropDownList ID="dropComponent" runat="server" DataSourceID="SqlDataSource01" DataTextField="orgName" DataValueField="orgID" AppendDataBoundItems="true" AutoPostback="true" OnSelectedIndexChanged="dropComponent_SelectedIndexChanged" SelectedValue='<%# Bind("orgID") %>' >
<asp:ListItem Value="" Text="-- Choose a component --" />
</asp:DropDownList>

/Carl.

by: DeMyuPosted on 2009-09-14 at 15:46:01ID: 25330002

carlnorrbom:

I finally got the application to work as intended. I thank you for your assistance and perseverance. Your most recent code above and information that I obtained from http://www.mikepope.com/blog/DisplayBlog.aspx?permalink=1629&count=no were very helpful. I have posted my working code below. I am sure it will come in handy for someone else.

DeMuy


<tr>
										<td class="formlabel"><LABEL class="reqlabel" for="dropComponent">Component:</LABEL><span class="form-required">*</span></td>
										<td align="left">
										<asp:DropDownList ID="dropComponent" runat="server" DataSourceID="SqlDataSource01" DataTextField="orgName" DataValueField="orgID" AppendDataBoundItems="true" AutoPostback="true" OnSelectedIndexChanged="dropComponent_SelectedIndexChanged" SelectedValue='<%# Bind("orgID") %>' >
                                            <asp:ListItem Value="" Text="-- Choose a component --" />
                                        </asp:DropDownList>	
									
		                           </td>
		                           <td><asp:RequiredFieldValidator runat="server" Display="Dynamic" ControlToValidate="dropComponent" ErrorMessage="<img src='images/common/required_trans.gif' align='absmiddle'>" />
									</td>
									</tr>
									<tr>
										<td class="formlabel"><LABEL class="reqlabel" for="dropApplication">Application:</LABEL><span class="form-required">*</span></td>
										<td align="left">										
											
									<asp:DropDownList ID="dropApplication" runat="server"  DataSourceID="AppSqlDS"   DataTextField="appName" DataValueField="appID" AppendDataBoundItems="true">
									<asp:ListItem Value="">
                                            -- Choose an Application --
                                        </asp:ListItem>
		                           </asp:DropDownList>		                           		                           
		                           <asp:SqlDataSource ID="AppSqlDS" runat="server" ConnectionString="<%$ ConnectionStrings:APPdbConnectString %>"
                                        SelectCommand="SELECT [appID], [appName] FROM [dbo].[applications] WHERE ([orgID] = @orgID)">
                                      <SelectParameters> 
                                      <asp:Parameter Name="orgID" Type="int32" />                           
                                                                                                             
                                       </SelectParameters>
                                   </asp:SqlDataSource>	
 
---- code behind
Protected Sub FormView1_DataBound(ByVal sender As Object, ByVal e As System.EventArgs) Handles FormView1.DataBound
 
        If FormView1.CurrentMode = FormViewMode.Edit Then
            Dim dv As System.Data.DataRowView = FormView1.DataItem
            Dim ddl2 As DropDownList = FormView1.FindControl("dropApplication")
            Dim dsc As SqlDataSource = FormView1.FindControl("AppSqlDS")
            dsc.SelectParameters("orgID").DefaultValue = dv("orgID")
            ddl2.DataBind()
            If Not IsDBNull(dv("appID")) Then
                ddl2.SelectedValue = dv("appID")
            End If
        End If
    End Sub
 
 
    Protected Sub dropComponent_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs)
 
        Dim dsc As SqlDataSource = CType(FormView1.FindControl("AppSqlDS"), SqlDataSource)
        Dim ddl1 As DropDownList = CType(FormView1.FindControl("dropComponent"), DropDownList)
        Dim ddl2 As DropDownList = CType(FormView1.FindControl("dropApplication"), DropDownList)
 
        ddl2.Items.Clear()
        ddl2.Items.Add(New ListItem("-- Choose an application --", ""))
        dsc.SelectParameters(0).DefaultValue = ddl1.SelectedValue
        ddl2.DataBind()
    End Sub
 
Protected Sub FormView1_ItemUpdating(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.FormViewUpdateEventArgs) Handles FormView1.ItemUpdating
                Dim dropComponent As DropDownList = CType(FormView1.FindControl("dropComponent"), DropDownList)
        Dim dropApplication As DropDownList = CType(FormView1.FindControl("dropApplication"), DropDownList)
 
                e.NewValues("appID") = dropApplication.SelectedValue
 
End Sub

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by: DeMyuPosted on 2009-09-14 at 15:47:04ID: 31627665

Thank you for the great work and assistance.

20120131-EE-VQP-002

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ASP.NET Formview control dropdownlist SelectedIndexChanged problem

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