Parser Error When Referring Control Value as ASPX Expression

Question

ASPX Code

<asp:RadioButtonList ID="rblApprovalSelection" runat="server" 
    <asp:ListItem Value="1">Item1</asp:ListItem>
    <asp:ListItem Value="2">Item2</asp:ListItem>
    <asp:ListItem Value="3" Selected="True">Item3</asp:ListItem>
    <asp:ListItem Value="4">Item4</asp:ListItem>
    <asp:ListItem Value="5">Item5</asp:ListItem>
</asp:RadioButtonList>

<asp:BoundField DataField="MyData" 
    Visible='<%#IIf(rblApprovalSelection.SelectedItem.Value=3, False, True) %>'
HeaderText="DataHeader" />

In my above code the below mentioned part is failed and throws error.

Visible='<%#IIf(rblApprovalSelection.SelectedItem.Value=3, False, True) %>'

As suggested by VDWWD the above code should be read as IF instead of IIF().

Error Message

Answer 1

Ok, you don't note/mention how you setting the value of the radio button list.

And since you want to hide/show the value, then I suggest better not to hide the cell, but hide a control in the cell (so it will not mess up grid formatting).

So, say this markup:

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"
    DataKeyNames="ID" CssClass="table table-hover" 
    Width="50%" OnRowDataBound="GridView1_RowDataBound">
    <Columns>
        <asp:BoundField DataField="Firstname" HeaderText="Firstname" />
        <asp:BoundField DataField="LastName" HeaderText="LastName" />
        <asp:BoundField DataField="City" HeaderText="From City" />
        <asp:TemplateField HeaderText="Status">
            <ItemTemplate>
                <asp:RadioButtonList ID="rblApprovalSelection" runat="server"
                    AutoPostBack="true" 
                    OnSelectedIndexChanged="rblApprovalSelection_SelectedIndexChanged" >
                    <asp:ListItem Value="1">Item1</asp:ListItem>
                    <asp:ListItem Value="2">Item2</asp:ListItem>
                    <asp:ListItem Value="3" Selected="True">Item3</asp:ListItem>
                    <asp:ListItem Value="4">Item4</asp:ListItem>
                    <asp:ListItem Value="5">Item5</asp:ListItem>
                </asp:RadioButtonList>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText ="Description">
            <ItemTemplate>
                <asp:Label ID="lblDesc" runat="server" 
                    Text='<%# Eval("Description") %>' ></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

So, note how I added a autopost-back for the RB list.

And our code to fill the gv is thus this:

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

    If Not IsPostBack Then

        LoadGrid

    End If

End Sub

Sub LoadGrid()

    Using conn As New SqlConnection(My.Settings.TEST4)
        Dim strSQL As String =
            "SELECT * FROM tblhotelsA ORDER BY HotelName"

        Using cmdSQL As New SqlCommand(strSQL, conn)
            conn.Open()
            Dim rstData As New DataTable
            rstData.Load(cmdSQL.ExecuteReader)
            GridView1.DataSource = rstData
            GridView1.DataBind()
        End Using
    End Using


End Sub

But, we need a row data bound event to hide/show that column based on RB seleting.

so, this:

Protected Sub GridView1_RowDataBound(sender As Object, e As GridViewRowEventArgs)

    If e.Row.RowType = DataControlRowType.DataRow Then

        Dim RB As RadioButtonList = e.Row.FindControl("rblApprovalSelection")
        Dim lblDesc As Label = e.Row.FindControl("lblDesc")

        lblDesc.Visible = RB.SelectedItem.Value <> 3
    End If

End Sub

And the code for the RB change is much the same as the row data binding.

So, this code:

Protected Sub rblApprovalSelection_SelectedIndexChanged(sender As Object, e As EventArgs)

    Dim RB As RadioButtonList = sender
    Dim gRow As GridViewRow = RB.NamingContainer
    Dim lblDesc As Label = gRow.FindControl("lblDesc")

    lblDesc.Visible = RB.SelectedItem.Value <> 3

End Sub

And thus we get this result:

So, for a standard GV, I suggest both the RB, and a label templated column, and not use cells (which are for defaulted databound columns). For any non "data bound" column, then you don't use cells, but can/should/will use findcontrol as per above.