[RESOLVED] Gridview and hidden columns

[a5m0d1]

I am populating a gridview from a database

 sql = "SELECT* FROM tblFaultlog ORDER BY sys_date ASC"
            GridView1.DataSource = sqlquery()
            GridView1.DataBind()

sqlquery return a datatable with the information I need, I do populate the datatable with some data but in the gridview I make one column.visable = false

Why is it that if it is not visable I can't call on that column progromatically?

it's as if the gridview doesn't retain the data for that column.

Thanks in advance.

[motil]

from what i remember once you make the column visible property to false the column is not been rendered and therefor you can get its data, try to get the data you want first and then set the column to hidden.

[gep13]

Pretty much exactly as motil as described.

If the column isn't set to visible, then it isn't rendered to the page, so there is no way for you to call into it programmatically, as it never goes into the ViewState for the page. If you keep a reference to the DataTable around though, you can still call into the columns of the DataTable if you need to.

Gary

[a5m0d1]

My datatable is populated via this function

  Function sqlquery() As DataTable
        Dim da As New OleDb.OleDbDataAdapter(sql, dbconn)
        dbconn.Open()
        da.Fill(ds, "fault")
        dbconn.Close()
        Maxrows = ds.Tables("fault").Rows.Count

        dt.Columns.Add(New DataColumn("Location", GetType(String)))
        dt.Columns.Add(New DataColumn("Staff_Member", GetType(String)))
        dt.Columns.Add(New DataColumn("Problem_Description", GetType(String)))
        dt.Columns.Add(New DataColumn("SYS_Date", GetType(String)))
        dt.Columns.Add(New DataColumn("ItemEffected", GetType(String)))
        dt.Columns.Add(New DataColumn("ImageURL", GetType(String)))
        dt.Columns.Add(New DataColumn("Work_done", GetType(String)))

        Dim dr As DataRow = dt.NewRow()
        inc = "0"

        For Each dr In ds.Tables("fault").Rows
            Dim imageurl As String
            If ds.Tables("fault").Rows(inc).Item(6) = "True" Then
                imageurl = "~/images/closed.png"
            Else
                imageurl = "~/images/open.png"
            End If

            dr = dt.NewRow()

            dr("Location") = ds.Tables("fault").Rows(inc).Item(1)
            dr("Staff_Member") = ds.Tables("fault").Rows(inc).Item(2).ToString
            dr("Problem_Description") = ds.Tables("fault").Rows(inc).Item(3)
            dr("SYS_Date") = ds.Tables("fault").Rows(inc).Item(4)
            dr("ItemEffected") = ds.Tables("fault").Rows(inc).Item(5)
            dr("ImageURL") = ResolveUrl(imageurl)
            dr("Work_Done") = ds.Tables("fault").Rows(inc).Item(7)
            dt.Rows.Add(dr)

            dr = dt.NewRow()
            inc = inc + 1

        Next
        ds.Clear()

        Return dt
    End Function

I have placed the datatable with the rest of my open variables at the top

Dim dt As New DataTable()

If I check dt.Rows.Count when within the sub that called sqlquery() then I get the correct data and everything is fine but when I try to access it from an event triggered by selecting a row in the gridview it shows as empty.

Why does it clear itself after being used in the initial sub?

[brin351]

You could add the hidden column field to the grid datakeys collection and access it from that collection. see here http://msdn.microsoft.com/en-us/libr....datakeys.aspx

Why are you hiding the column?

[motil]

again i have little knowledge with datasoruce/datatable/gridview since i'm not using those controls (rarely i use gridview) but in the line of code just about your "return dt" you got this line:

ds.Clear()

i think this method of the datasource will clear all the data (datatable included) that stored inside the datasource and that the reason you have empty datatables, but you might want to wait for Gary and hear his opinion.

[a5m0d1]

I use the Dataset DS to populate my Datatable, I did try and remove the clear but still 0.

Just read that having

Dim dt as New DataTable

is why it resets? makes some sence but when I change it to

Dim dt as Datatable

I get error "object reference not set, etc etc"

Going to look at grid datakeys collection now
I need to hide some of the information as its just not needed by the user but when they click on certain things it will use that data and the rest of the data on that selected row to calculate a result.

[a5m0d1]

Dont think I can use datakeyname as it is the primary key and some of my rows contain the same data.

[a5m0d1]

Ahh, if I don't clear the DS I can still use it. Changed out the Datatable for the Datasource.
But I still get that dam error I so love "Object reference not set to an instance of an object."

[a5m0d1]

Fixed it

Shared dt As DataTable

Now I can access it in my other subs

Thanks for your help all