How do I retrieve data from a hidden column in GridView? VB - asp.net

Question

I'm kind of stuck here, after doing some research I can't seem to find an answer. Anyway I don't know how can I retrieve the Primary key in my Gridview hidden column.
Here is my gridview
<asp:GridView ID="grdDent" runat="server" AutoGenerateColumns="False" Width="852px" DataKeyNames="app_id">
<Columns>
<asp:TemplateField>
<EditItemTemplate>
<asp:CheckBox ID="chkApp" runat="server" />
</EditItemTemplate>
<ItemTemplate>
<asp:CheckBox ID="chkApp" runat="server" />
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="app_id" HeaderText="app_id" Visible="False" />
<asp:BoundField DataField="app_date" HeaderText="Date" SortExpression="Date" />
<asp:BoundField DataField="app_time" HeaderText="Time" SortExpression="Time" />
<asp:BoundField DataField="app_rsn" HeaderText="Reason" SortExpression="Reason" />
<asp:BoundField DataField="app_info" HeaderText="Comment" SortExpression="Comment" />
<asp:BoundField DataField="app_sts" HeaderText="Status" SortExpression="Status" />
<asp:BoundField DataField="Patient" HeaderText="Requested by" SortExpression="Patient" />
<asp:BoundField DataField="app_timestamp" HeaderText="Date requested" SortExpression="Date requested" />
</Columns>
</asp:GridView>
And here is my code at button click
For Each row As GridViewRow In grdDent.Rows
If row.RowType = DataControlRowType.DataRow Then
Dim chkApp As CheckBox = TryCast(row.Cells(0).FindControl("chkApp"), CheckBox)
If chkApp.Checked Then
cmd = New MySqlCommand("UPDATE appointment_table SET app_sts = 'Approved' WHERE app_id = #p1", con)
cmd.Parameters.AddWithValue("#p1", row.Cells(1).Text)
con.Open()
cmd.ExecuteNonQuery()
con.Close()
End If
End If
Next
Here is my code to fill up the gridview
Using cmd = New MySqlCommand("SELECT app_id, app_date, app_time, app_rsn, app_info, app_sts, group_concat(pat_lname, pat_fname) As Patient, app_timestamp FROM appointment_table INNER JOIN patient_table WHERE app_sts = 'Queue'", con)
con.Open()
Dim ds As New DataSet()
Dim a As New MySqlDataAdapter(cmd)
a.Fill(ds)
grdDent.DataSource = ds
grdDent.DataBind()
con.Close()
End Using
The problem now is that whenever I click the button, it would not do anything, not even show an error, so I do not know what to do.

Answer 1

First debug the code and check from which line you are getting the error.
Also try following code.
.HideData
{
display: none;
}
Replace your app_id bound field like as below.
Don't use visible false property.

Answer 2

when you set visible=false that column will not rendered in gridview's html.
so, instead of visible=false make its style='display:none'
use like this :
<asp:BoundField DataField="ItemDesc" HeaderText="app_id" >
<ItemStyle CssClass="hidden"/>
</asp:BoundField>
<style type="text/css">
.hidden
{
display:none;
}
</style>
and use this in your foreach loop
dim appid as string
appid=row.Cells(1).Text

Answer 3

I see that you store the primary key in DataKeyNames="app_id"
so you would grab that in code with
grdDent.DataKeys.Item(a row index here).Value
You can drop the BoundField holding this value. It being "Visible=False" will not hold any value.

Answer 4

The way I do it is like this..
1st remove your boundfield and just add a lable to one of the template fields like this.
<asp:GridView ID="grdDent" runat="server" AutoGenerateColumns="False" Width="852px" DataKeyNames="app_id">
<Columns>
<asp:TemplateField>
<EditItemTemplate>
<asp:CheckBox ID="chkApp" runat="server" />
</EditItemTemplate>
<ItemTemplate>
<asp:CheckBox ID="chkApp" runat="server" />
<asp:Label ID="lblApp_ID" Visible="False" runat="server" Text='<%# Bind("app_id") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="app_date" HeaderText="Date" SortExpression="Date" />
<asp:BoundField DataField="app_time" HeaderText="Time" SortExpression="Time" />
<asp:BoundField DataField="app_rsn" HeaderText="Reason" SortExpression="Reason" />
<asp:BoundField DataField="app_info" HeaderText="Comment" SortExpression="Comment" />
<asp:BoundField DataField="app_sts" HeaderText="Status" SortExpression="Status" />
<asp:BoundField DataField="Patient" HeaderText="Requested by" SortExpression="Patient" />
<asp:BoundField DataField="app_timestamp" HeaderText="Date requested" SortExpression="Date requested" />
</Columns>
</asp:GridView>
by doing this it will put the label in each row but it wont show up to the user and the part that says "Text='<%# Bind("app_id") %>'" that binds the text to that label in each row.
Now for the code on the button click you should use this:
Dim i As Integer = 0
Dim app_ID As Integer '<- I was using an integer but you can use any datatype
For Each row As GridViewRow In grdDent.Rows
If CType(row.FindControl("chkApp"), CheckBox).Checked = True Then
app_ID = CType(grdDent.Rows(i).FindControl("lblApp_ID"), Label).Text
cmd = New MySqlCommand("UPDATE appointment_table SET app_sts = 'Approved' WHERE app_id =" & app_ID , con)
con.Open()
cmd.ExecuteNonQuery()
con.Close()
End If
i += 1
Next
All of this has worked for me, so I hope it works for you!

Answer 5

You can use something like this:
For Each row As GridViewRow In yourgrid.Rows
Dim chk As CheckBox = CType(row.FindControl("chkApp"), CheckBox)
If chk IsNot Nothing And chk.Checked Then
'get your selected row data here and perform update operation
End If
Next row
NOTE: My suggestion is to first debug the code and make sure your code is working fine and method is calling perfectly.
You can check getting asp.net gridview selected row data from server-side to get more details.
Hope it helps you!