How to enable and disable buttons in a gridview in asp.net - asp.net

Question

I currently have a GridView with two buttons that I have added using the following code;
<asp:GridView ID="gvResults" AutoGenerateColumns="False" runat="server" Font-Size="small"
DataKeyNames="BeachHutID" OnRowDataBound="gvResults_RowDataBound" CssClass="BBCSearch">
<Columns>
<asp:BoundField DataField="BeachHutID" SortExpression="BeachHutID" Visible="false">
</asp:BoundField>
<asp:ImageField DataImageUrlField="HutImage" ItemStyle-Width="1%" ReadOnly="true" />
<asp:BoundField HeaderText="Facilities" DataField="Facilities" Visible="false"></asp:BoundField>
<asp:BoundField HeaderText="Info" DataField="Info" Visible="false"></asp:BoundField>
<asp:TemplateField>
<ItemTemplate>
<asp:PlaceHolder ID="lblHolder" runat="server"></asp:PlaceHolder>
<br />
<asp:PlaceHolder ID="imgHolder" runat="server"></asp:PlaceHolder>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField>
<ItemTemplate>
<asp:Button ID="btnHire" CommandArgument='<%# Eval("BeachHutID") %>' runat="server"
Text="Hire Beach Hut" OnClick="Hire_Click" />
<asp:Button ID="ButtonLogin" CommandArgument='<%# Eval("BeachHutID") %>' runat="server"
Text="Login to Hire Beach Hut" OnClick="Login_Redirect" />
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
What I want to happen is if the user is logged in, the btnHire button should be enabled and showing and if they're not logged in, ButtonLoggedIn is showing and btnHire is hidden. This is the code I have at the moment;
Public Sub PopulateGrid()
Dim AvailableHuts As New DataTable
AvailableHuts = GetData()
gvResults.DataSource = AvailableHuts
gvResults.DataBind()
gvResults.Enabled = True
'If statement controlling the enabling and disabling of the Beach Hut booking button
If Session("LoginID") = "" Then
For Each rowItem As GridViewRow In gvResults.Rows
rowItem.Cells(5).Enabled = True
Next
End If
lblCaption.Text = "Your search returned " + CStr(AvailableHuts.Rows.Count) + " results"
End Sub
At the moment both buttons are enabled at all times and I'm not sure what I need to add/changed to get the desired result.
From the answer posted by #Andrei, I have added the following to to this Sub;
Protected Sub gvResults_RowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs) Handles gvResults.RowDataBound
Dim URL(), Text() As String
Dim img As Image
Dim lbl As Label
Dim FacilitiesImg As PlaceHolder = e.Row.FindControl("imgHolder")
Dim Infolbl As PlaceHolder = e.Row.FindControl("lblHolder")
'Added Code from answer
Dim hireBtn As Button = CType(e.Row.FindControl("btnHire"), Button)
hireBtn.Visible = Not String.IsNullOrEmpty(Session("LoginID"))
'Added Code from answer
Dim LoginBtn As Button = CType(e.Row.FindControl("ButtonLogin"), Button)
LoginBtn.Visible = String.IsNullOrEmpty(Session("LoginID"))
If e.Row.RowType = DataControlRowType.DataRow Then
URL = e.Row.DataItem(3).Split(",")
Text = e.Row.DataItem(2).Split(",")
'Add the Facilities Images to the grid Row
For Each item In URL
If item.ToString <> "" Then
img = New Image
img.ImageUrl = item.ToString
FacilitiesImg.Controls.Add(img)
End If
Next
'Add the information to the grid row
'convert # into a carriage return and * into £
For Each item In Text
If item.ToString <> "" Then
lbl = New Label
lbl.Text = Replace(Replace(item.ToString, "#", "<br />"), "*", "£")
Infolbl.Controls.Add(lbl)
End If
Next
End If
End Sub
However I'm receiving the following error when trying to run the program;
Cannot refer to an instance member of a class from within a shared method or shared member initializer without an explicit instance of the class
Any assistance would be much appreciated.
Thanks

Answer 1

Not sure how is your authentication implemented, but let's assume you use HttpContext.Current.Request.IsAuthenticated. Then you can just manipulate Visible property of the buttons in code behind:
btnHire.Visible = HttpContext.Current.Request.IsAuthenticated
ButtonLoggedIn.Visible = Not HttpContext.Current.Request.IsAuthenticated
Update.
Sorry, somehow missed from the post the fact that you seems to be using Session("LoginID") to decide if the use is logged in. The you can do this:
btnHire.Visible = Not String.IsNullOrEmpty(Session("LoginID"))
ButtonLoggedIn.Visible = String.IsNullOrEmpty(Session("LoginID"))
Update 2.
As it turns out, buttons are a part of GridView row. As they are inside the template, you cannot really reach them in the code behind. So you can take two options.
First, you can subscribe to RowDataBound event (which you already did), and inside it do FindControl in the current row to find the necessary button:
Sub gvResults_RowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
...
Button hireBtn = CType(e.Row.FindControl("btnHire"), Button);
hireBtn.Visible = Not String.IsNullOrEmpty(Session("LoginID"))
and likewise for the second button.
Second, you can try doing it in the markup:
<asp:Button ID="btnHire" CommandArgument='<%# Eval("BeachHutID") %>'
runat="server" Text="Hire Beach Hut" OnClick="Hire_Click"
Visible=<%# String.IsNullOrEmpty(Session("LoginID")) %> />

Answer 2

try
<asp:Button ID="btnHire" CommandArgument='<%# Eval("BeachHutID") %>' runat="server" Visible='<%# islogin()?true:false %>' Text="Hire Beach Hut" OnClick="Hire_Click" />
<asp:Button ID="ButtonLoggedIn" CommandArgument='<%# Eval("BeachHutID") %>' runat="server" Visible='<%# islogin()?false:true %>' Text="Login to Hire Beach Hut" OnClick="Login_Redirect" />
paste this code to aspx.cs page:
Public Shared Function isLogin() As Boolean
Dim stat As Boolean = False
Try
If Session("LoginID") IsNot Nothing AndAlso Session("LoginID") <> "" Then
stat = True
End If
Catch e1 As Exception
stat = False
End Try
Return stat
End Function
Edit2:
Visible='<%# islogin()?false:true %> this means if isLogin() return true then Visible property set to false else it's visible property set to true.