Fetching Null Values of GUID ,when selction is made in Grdiview

Hi SaraBob,
For some reason, your GUID is wrong (eee000317-aa7e-46ca-a329-0fdac6411ead). It should be 8-4-4-12 characters, not 9-4-4-12
It should work this way (if you have the right GUID):
 Dim LocId As Guid = CType(Me.GrdLocation.DataKeys(e.NewSelectedIndex)("LocID"), Guid)
Label1.Text = LocId.ToString
 For testing purposes, try to declare LocId like this (note the 8-4-4-12 format):
Dim LocId As New Guid("ee000317-aa7e-46ca-a329-0fdac6411ead")
Label1.Text = LocId.ToString

Hi Juan barrera,

"For some reason, your GUID is wrong (eee000317-aa7e-46ca-a329-0fdac6411ead). It should be 8-4-4-12 characters, not 9-4-4-12"
I checked in the database, the GUID is 8-4-4-4-12.I had made a mistake, when i pasted it here , i suppose.

I did as you said for testing purposes,still my GUID comes as follows:
00000000-0000-0000-0000-000000000000
I have attached a file(.doc), which shows the Event page and code behind.The 00000-0000-0000-000...
Shows the label content.You can see the LocId, which has 8-4-4-4-12.
please have a look at it and help me with this code.

Event.bmp

Sorry..that was only a bmp file..Not Doc.. I wil test for your solution right now

This is the error i'm getting ,
System.NullReferenceException: Object reference not set to an instance of an object.
Pointing to to this line:
  Dim s As String = LocId.ToString()

So i you said, the datakeys are fetvhing Null values..
What shoukd be done

Hi SaraBob,

Try by calling GrdLocation.DataBind() before the DataKeys. I guess that, however you are binding the grid, it hasn't been data-bound yet when you try to access the collection.

GrdLocation.DataBind()
Dim LocId As Object = Me.GrdLocation.DataKeys(e.NewSelectedIndex)("LocID")
Dim s as String = LocId.ToString()

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Hey Juan_Barrera:
Thanks for the quick reply.I really appreciated it.As this has to deliverered by EOB, i'm struggling, as your helping me out.I appreciate your patience.

I have pasted the code, whats happening here :
// This code behind is for On click of a button, i make the gridview=true, filling it with datasource
Protected Sub btnLocation_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnLocation.Click
        GrdLocation.Visible = True
        Dim MyCompCommand As SqlDataAdapter = New SqlDataAdapter("Select Locations.LocId,Locations.LocationName As Location,Locations.City,Locations.State,StateProvince.Countryregionname as Country from Locations,Stateprovince where Locations.Stateprovinceid=StateProvince.Stateprovinceid order By LocationName ASC", MyConn)

        Dim DS As DataSet = New DataSet()
        MyCompCommand.Fill(DS, "Locations")

        GrdLocation.DataSource = DS.Tables("Locations").DefaultView
        GrdLocation.DataBind()
        MyConn.Close()
    End Sub
 
// This is the code for Selecting the GUID
    Sub GrdLocation_SelectedIndexChanging(ByVal sender As Object, ByVal e As GridViewSelectEventArgs)

        'Dim LocId As Guid = CType(Me.GrdLocation.DataKeys(e.NewSelectedIndex)("LocID"), Guid)
        'Dim Loc As String = Me.GrdLocation.DataKeys(e.NewSelectedIndex)("Location")
        'Label1.Text = Convert.ToString(LocId)
        GrdLocation.DataBind()
        Dim LocId As Object = Me.GrdLocation.DataKeys(e.NewSelectedIndex)("LocID")
        Dim s As String = LocId.ToString()

        Label1.Text = s.ToString
        GrdLocation.Visible = False
  End Sub

When i did databindbefore the datakeys collection, i got a error loke :System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
pointing to datakeys fetching part

Sara, you should rebind the grid on every postback, don't do it only onButtonClick:

Protected Sub BindGrid()
 
        Dim MyCompCommand As SqlDataAdapter = New SqlDataAdapter("Select Locations.LocId,Locations.LocationName As Location,Locations.City,Locations.State,StateProvince.Countryregionname as Country from Locations,Stateprovince where Locations.Stateprovinceid=StateProvince.Stateprovinceid order By LocationName ASC", MyConn)
 
        Dim DS As DataSet = New DataSet()
        MyCompCommand.Fill(DS, "Locations")
 
        GrdLocation.DataSource = DS.Tables("Locations").DefaultView
        GrdLocation.DataBind()
        MyConn.Close()
    End Sub
 
 
Protected Sub GrdLocation_SelectedIndexChanging(ByVal sender As Object, ByVal e As GridViewSelectEventArgs) Handles GrdLocation.SelectedIndexChanging
        BindGrid()
        Dim LocId As Guid = CType(Me.GrdLocation.DataKeys(e.NewSelectedIndex)("LocID"), Guid)
        Dim Loc As String = Me.GrdLocation.DataKeys(e.NewSelectedIndex)("Location").ToString
        Label1.Text = Loc
        GrdLocation.Visible = False
  End Sub

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As you said i did databind on every postback.,Sorry Not working..I'm Still getting NULL values :((

I have an observation here,:
But even before i did the databind( i mean in earlier snippet), i could get the Location(spain,Orlando etc) into the textbox, but not LocId(which was null).
So, even without doing this Databinding on every postback,i could get the location.
Comment ?!

You can get the location because the controls collection is populated, but not the DataKeys collection.
Still is odd that the DataKeys() is empty. Can you use the textbox values? It's got the side benefit of reducing ViewState size by eliminating one item from the DataKeys.

I have set Location also as datakey..Is that creating problems?
" Can you use the textbox values? It's got the side benefit of reducing ViewState size by eliminating one item from the DataKeys."
Is this what you mean txtLocId.Text=LocId ...????

<asp:GridView ID="GrdLocation" runat="server" 
DataKeyNames="LocId,Location" 
autogeneratecolumns="false" AutoGenerateSelectButton="True" 
onselectedindexchanging="GrdLocation_SelectedIndexChanging" AllowPaging="True" 
AllowSorting="True"> 
<columns> 
<asp:commandfield showselectbutton="true" 
headertext="Select Location"/> 
<asp:boundfield datafield="LocId" 
headertext="LocId"/> 
<asp:boundfield datafield="Location" 
headertext="Location"/> 
<asp:boundfield datafield="City" 
headertext="City"/> 
<asp:boundfield datafield="State" 
headertext="State"/> 
<asp:boundfield datafield="Country" 
headertext="Country"/> 
</columns> 
 
</asp:GridView> 

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Yes, that's what I mean: Use the TextBox value to retrieve the information you need, instead of using DataKeys.
Is not that it should create problems, is just that if you already have the information you can save you trouble and ViewState space by not using DataKeys()

But the LocId is in the Gridview. as datakey.The user needs to select value from Gridview.

But isn't it in a field as well?:

<asp:boundfield datafield="LocId" headertext="LocId"/>

Yes..it is in Bound field..So i will fetch in a textbox?

Hi lem2802:
 Its on gridview_GrdLocation_SelectedIndexChanging event..

I mean Its gridview_selectedchanging event

and how thw user "select a location"... pressing one button??

Yes , The user slects a location , by pressing a Select location button:i bind the gridview in the button _click event.
Then on selectedchanging event gridview, i select the LociD( which is hidden, set as datakey) and  (trying) to put in a textbox.
I have attached the Code snippet of on buttonclick , on selected changing and the gridview.
Please help.

 Protected Sub btnLocation_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnLocation.Click
        GrdLocation.Visible = True
        Dim MyCompCommand As SqlDataAdapter = New SqlDataAdapter("Select Locations.LocId,Locations.LocationName As Location,Locations.City,Locations.State,StateProvince.Countryregionname as Country from Locations,Stateprovince where Locations.Stateprovinceid=StateProvince.Stateprovinceid order By LocationName ASC", MyConn)
 
        Dim DS As DataSet = New DataSet()
        MyCompCommand.Fill(DS, "Locations")
 
        GrdLocation.DataSource = DS.Tables("Locations").DefaultView
        GrdLocation.DataBind()
        MyConn.Close()
    End Sub
'Selected changing event
 Sub GrdLocation_SelectedIndexChanging(ByVal sender As Object, ByVal e As GridViewSelectEventArgs)
 
        Dim LocId As Guid = CType(Me.GrdLocation.DataKeys(e.NewSelectedIndex)("LocID"), Guid)
        Dim Loc As String = Me.GrdLocation.DataKeys(e.NewSelectedIndex)("Location")
        'Label1.Text = Convert.ToString(LocId)
 
        'Dim LocId As Object = Me.GrdLocation.DataKeys(e.NewSelectedIndex)("LocID")
        'Dim s As String = LocId.ToString()
 
        'Label1.Text = s.ToString
        TxtLocation.Text = Loc.ToString
        Dim s As String = LocId.ToString()
 
        TextBox1.Text = s.ToString
        GrdLocation.Visible = False
'Asp Page of the gridview
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
                <asp:GridView ID="GrdLocation" runat="server" 
                DataKeyNames="LocId,Location"
                autogeneratecolumns="false" AutoGenerateSelectButton="True"
                onselectedindexchanging="GrdLocation_SelectedIndexChanging" AllowPaging="True" 
                    AllowSorting="True">
                <columns>
          <asp:commandfield showselectbutton="true"
            headertext="Select Location"/>
          <asp:boundfield datafield="LocId"
            headertext="LocId"/>
          <asp:boundfield datafield="Location"
            headertext="Location"/>
          <asp:boundfield datafield="City"
            headertext="City"/>
          <asp:boundfield datafield="State"
            headertext="State"/>
          <asp:boundfield datafield="Country"
            headertext="Country"/>
        </columns>
                    
                </asp:GridView>

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ok... now try tu use the event "SelectedIndexChanged" instead "SelectedIndexChanging"

After changing everything to on SelectedChanged
i get this error
e.NewSelectedIndex is not a member of event args..
can you please look at the earlier code in selected eventchanging, and let me know what should be changed...PLEASE

use "GrdLocation.SelectedIndex" instead "e.NewSelectedIndex"

I have this error gazillion times..." Value of type 'String' cannot be converted to 'System.Guid'
Pointing to :
Dim LocId As Guid = CType(Me.GrdLocation.Rows(GrdLocation.SelectedIndex).Cells(1).Text, Guid)
If i try to correct it, the guid fetches NULL value...
I'm in need of urgent help to solve this..

not this...

Dim LocId As Guid = CType(Me.GrdLocation.Rows(
GrdLocation.SelectedIndex).Cells(1).Text, Guid)

use this...

 Dim LocId As Guid = CType(Me.GrdLocation.DataKeys(GrdLocation.SelectedIndex)("LocID"), Guid)

Well i had tried this earlier also..I did it again..But its fetching Null on GUIDs..
both SelectedIndexchanging and  Selectedindexchanged....fetched NULL values
help me...

ok... may be you have a viewstate problem... try filling the grid in the page_load... and tell me what happen...

I dont think its a view state problem...Beacuse if i try to get location( spain,orlando) from the gridview 2 nd cell, i would get that.Its only problem with GUIds

Hi

try this sample code

aspx

<%@ Page Language="VB" AutoEventWireup="false" CodeFile="DataGrid.aspx.vb" Inherits="Data_DataGrid" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <asp:GridView ID="GrdLocation" runat="server"
DataKeyNames="LocId,Location"
autogeneratecolumns="false" AutoGenerateSelectButton="True"
onselectedindexchanging="GrdLocation_SelectedIndexChanging" AllowPaging="True"
AllowSorting="True">
<columns>
<asp:commandfield showselectbutton="true"
headertext="Select Location"/>
<asp:boundfield datafield="LocId"
headertext="LocId"/>
<asp:boundfield datafield="Location"
headertext="Location"/>
<asp:boundfield datafield="City"
headertext="City"/>
<asp:boundfield datafield="State"
headertext="State"/>
<asp:boundfield datafield="Country"
headertext="Country"/>
</columns>
 
</asp:GridView>
        <asp:TextBox ID="TextBox1" runat="server" Width="489px"></asp:TextBox>
        <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
    </form>
</body>
</html>


code behind


Partial Class Data_DataGrid
    Inherits System.Web.UI.Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        If (Not Me.IsPostBack) Then
            Me.GrdLocation.DataSource = clsData.GetDataTable
            Me.GrdLocation.DataBind()
        End If
    End Sub

    Protected Sub GrdLocation_SelectedIndexChanging(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewSelectEventArgs) Handles GrdLocation.SelectedIndexChanging
        Dim gid As Guid = CType(Me.GrdLocation.DataKeys(e.NewSelectedIndex)("LocId"), Guid)
        Me.TextBox1.Text = gid.ToString
        Me.TextBox2.Text = Me.GrdLocation.DataKeys(e.NewSelectedIndex)("Location").ToString


    End Sub
End Class



app_code


Imports System.Data

Public Class clsData
    Public Shared Function GetDataTable() As DataTable
        Dim dt As New DataTable
        dt.Columns.Add("LocId", GetType(Guid))
        dt.Columns.Add("Location")
        dt.Columns.Add("City")
        dt.Columns.Add("State")
        dt.Columns.Add("Country")

        dt.Rows.Add(New Object() {System.Guid.NewGuid, "aaaaa", "aaaaaaaaa", "aaaaaaaaaaaa", "aaaaaaaaaaaa"})
        dt.Rows.Add(New Object() {System.Guid.NewGuid, "bbbbb", "bbbbbbbbb", "bbbbbbbbbbbb", "bbbbbbbbbbbb"})
        dt.Rows.Add(New Object() {System.Guid.NewGuid, "ccccc", "ccccccccc", "cccccccccccc", "cccccccccccc"})
        dt.Rows.Add(New Object() {System.Guid.NewGuid, "ddddd", "ddddddddd", "dddddddddddd", "dddddddddddd"})

        Return dt
    End Function


    Public Shared Function GetDataTable1() As DataTable
        Dim dt As New DataTable
        dt.Columns.Add("LocId")
        dt.Columns.Add("Location")
        dt.Columns.Add("City")
        dt.Columns.Add("State")
        dt.Columns.Add("Country")

        dt.Rows.Add(New Object() {1, "aaaaa", "aaaaaaaaa", "aaaaaaaaaaaa", "aaaaaaaaaaaa"})
        dt.Rows.Add(New Object() {2, "bbbbb", "bbbbbbbbb", "bbbbbbbbbbbb", "bbbbbbbbbbbb"})
        dt.Rows.Add(New Object() {3, "ccccc", "ccccccccc", "cccccccccccc", "cccccccccccc"})
        dt.Rows.Add(New Object() {4, "ddddd", "ddddddddd", "dddddddddddd", "dddddddddddd"})

        Return dt
    End Function

End Class

please see this in ur code

    Dim LocId As Guid = CType(Me.GrdLocation.DataKeys(e.NewSelectedIndex)("LocID"),

 <asp:boundfield datafield="LocId"  headertext="LocId"/>

see the LocID case with LocId

Hi madhaven_Pillai,
That way code will be long and uneasy to handle it for GUIDs.
We , here as team tried for long hrs
This is the solution we finnaly agreed on and the guid problem.

Sub GrdLocation_RowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
' *********************************************************************
' Column #0 = Select button
' Column #1 = LocID
' Column #2 = Location
' Column #3 = Destination
' Hide the LocID column...
' *********************************************************************

If e.Row.RowType = DataControlRowType.DataRow Then
e.Row.Cells(1).Style.Add("display", "none")
ElseIf e.Row.RowType = DataControlRowType.Header Then
e.Row.Cells(1).Style.Add("display", "none")
ElseIf e.Row.RowType = DataControlRowType.Footer Then
e.Row.Cells(1).Style.Add("display", "none")
End If
End Sub

Protected Sub GrdLocation_SelectedIndexchanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles GrdLocation.SelectedIndexChanged
' *********************************************************************
' Column #0 = Select button
' Column #1 = TravelLocID
' Column #2 = Name
' Column #3 = Destination
' *********************************************************************
' Get the currently selected row...
Dim gridRow As GridViewRow = GrdLocation.SelectedRow
' Set the TextBox to the Destination value in the currently selected row...
TxtLocation.Text = gridRow.Cells(2).Text
HiddenLocid.Value = gridRow.Cells(1).Text =====This is how we got the guid in a hidden field.
GrdLocation.Visible = False
End Sub