GridView is not allowing to find any control - html

Question

I want to use nested gridview. But my Parent Grid is showing Nothing in ChildGrid's variable.
Any help? I've tried following ways:
1)
Dim gvChild As GridView =
CType(Me.gvwSubjectForProject.FindControl("gvChildGrid"), GridView)
2)
Dim gvChild As GridView =
Me.gvwSubjectForProject.FindControl("gvChildGrid")
gvChild.DataSource = dt_Subject
gvChild.DataBind()
I want to find Child grid's id and then want to assign it data source.
VB
Private Function FillGrid(ByVal mode As String, ByVal dt_Subject As
DataTable) As Boolean
'Dim dt_Subject As DataTable = Nothing
'Dim dt_sortsubject As DataTable = Nothing
Try
If (mode = "ParentGrid") Then
Me.gvwSubjectForProject.DataSource = Nothing
Me.gvwSubjectForProject.DataBind()
'Me.ViewState(VS_CurrentSubject) = Nothing
Me.btnExport.Visible = False
'dt_Subject.Columns.Add("Status", GetType(String))
If Not dt_Subject Is Nothing Then
If dt_Subject.Rows.Count > 0 Then
If dt_Subject.Rows.Count > 0 Then
For Each dr_Row In dt_Subject.Rows
If dr_Row("cStatus") = "AC" Then
dr_Row("Status") = "Active"
ElseIf dr_Row("cStatus") = "IA" Then
dr_Row("Status") = "In Active"
ElseIf dr_Row("cStatus") = "HO" Then
dr_Row("Status") = "Hold"
ElseIf dr_Row("cStatus") = "SC" Then
dr_Row("Status") = "Screened"
ElseIf dr_Row("cStatus") = "BO" Then
dr_Row("Status") = "Booked"
ElseIf dr_Row("cStatus") = "OS" Then
dr_Row("Status") = "On Study"
ElseIf dr_Row("cStatus") = "FI" Then
dr_Row("Status") = "Forever Ineligible"
Else
dr_Row("cStatus") = "Not Found"
End If
Next
Me.btnExport.Visible = True
'Me.ViewState(VS_CurrentSubject) = dt_Subject
Me.gvwSubjectForProject.DataSource = dt_Subject
Me.gvwSubjectForProject.DataBind()
End If
End If
End If
ElseIf (mode = "ChildGrid") Then
If Not dt_Subject Is Nothing Then
If dt_Subject.Rows.Count > 0 Then
'Me.gvwSubjectForProject.DataSource = dt_Subject
'Me.gvwSubjectForProject.DataBind()
'Me.gvwSubjectForProject.FindControl("gvChildGrid").DataSource =
dt_Subject
'CType(Me.gvwSubjectForProject.FindControl("gvChildGrid"),
GridView).DataBind()
'Me.gvwSubjectForProject.FindControl("gvChildGrid").
'Me.gvwSubjectForProject.FindControl("gvChildGrid").DataBind()
Dim gvChild As GridView = Me.gvwSubjectForProject.FindControl("gvChildGrid")
gvChild.DataSource = dt_Subject
gvChild.DataBind()
End If
End If
End If
Return True
Catch ex As Exception
Me.ShowErrorMessage("Error While Binding Grid", "....FillGrid")
Return False
End Try
End Function
HTML NESTED GRIDVIEW
<asp:Panel ID="pnlgvwSubjectStatus" runat="server" Style="max-height: 500px; overflow: auto;
width: 60%;">
<asp:GridView ID="gvwSubjectForProject" runat="server" AutoGenerateColumns="false"
SkinID="grdViewSmlAutoSize" Width="70%" ShowFooter="true" AllowPaging="true"
PageSize="1">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<asp:ImageButton ID="imgbtnExpand" runat="server" ImageUrl="../images/Plus.gif" alt="Expand"
OnClientClick="imgbtnExpand_Click" />
<asp:HiddenField ID="hcStatus" runat="server" Value='<%# Eval("cStatus") %>' />
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="Status" HeaderText="STATUS">
<ItemStyle HorizontalAlign="Left" VerticalAlign="Middle" Wrap="true" Width="40%" />
<HeaderStyle HorizontalAlign="Center" VerticalAlign="Middle" Wrap="true" Width="40%" />
</asp:BoundField>
<asp:TemplateField>
<ItemTemplate>
<div style="max-height: 300px; width: 100%; overflow: auto;
text-align: right;">
<%--<asp:Panel ID="pnlOrders" runat="server" Width="100%">--%>
<asp:GridView ID="gvChildGrid" runat="server" AutoGenerateColumns="false" SkinID="grdViewSmlAutoSize">
<Columns>
<asp:BoundField ItemStyle-Width="40%" DataField="vSubjectID" HeaderText="SUBJECT ID">
<ItemStyle HorizontalAlign="Left" VerticalAlign="Middle" Wrap="true" Width="40%" />
<HeaderStyle HorizontalAlign="Center" VerticalAlign="Middle" Wrap="true" Width="40%" />
</asp:BoundField>
<asp:BoundField ItemStyle-Width="60%" DataField="FullName" HeaderText="FULL NAME">
<ItemStyle HorizontalAlign="Left" VerticalAlign="Middle" Wrap="true" Width="60%" />
<HeaderStyle HorizontalAlign="Center" VerticalAlign="Middle" Wrap="true" Width="60%" />
</asp:BoundField>
</Columns>
</asp:GridView>
<%--</asp:Panel>--%>
</div>
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="TotalSubject" HeaderText="TOTAL SUBJECTS">
<ItemStyle HorizontalAlign="Left" VerticalAlign="Middle" Wrap="true" Width="50%" />
<HeaderStyle HorizontalAlign="Center" VerticalAlign="Middle" Wrap="true" Width="50%" />
</asp:BoundField>
</Columns>
</asp:GridView>
</asp:Panel>
And one more thing, in HTML when child gridview is not displayed, its still filling while creating its DOM. I want to delete that blank space too.

Answer 1

Your posted code is not working, because you are using the FindControl() method on the entire parent grid view control instead of on an individual row in the grid view control, like this:
Find child grid view in OnRowDataBound event:
Sub ParentGridView_RowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
' Only look for child grid view in data rows, ignore header and footer rows
If e.Row.RowType = DataControlRowType.DataRow Then
Dim theChildGridView As GridView = DirectCast(e.Row.FindControl("gvChildGrid"), GridView)
' Do something with theChildGridView here
End If
End Sub
Find child grid view by looping through all rows in parent grid view control:
For Each row As GridViewRow In ParentGridView.Rows
' Only look for child grid view in data rows, ignore header and footer rows
If row.RowType = DataControlRowType.DataRow Then
Dim theChildGridView As GridView = DirectCast(row.FindControl("gvChildGrid"), GridView)
' Do something with theChildGridView here
End If
Next