ASP.NET using Bind/Eval in .aspx in If statement

Question

in my .aspx I'm looking to add in an If statement based on a value coming from the bind. I have tried the following:

<% if(bool.Parse(Eval("IsLinkable") as string)){ %>                    
        monkeys!!!!!!
        (please be aware there will be no monkeys, 
        this is only for humour purposes)
 <%} %>

IsLinkable is a bool coming from the Binder. I get the following error:

InvalidOperationException
Databinding methods such as Eval(), XPath(), and Bind() can only
be used in the context of a databound control.

Bazzz · Accepted Answer · 2011-04-10T14:33:11.967

20

You need to add your logic to the ItemDataBound event of ListView. In the aspx you cannot have an if-statement in the context of a DataBinder: <%# if() %> doesn't work.

Have a look here: http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.listview.itemdatabound.aspx

The event will be raised for each item that will be bound to your ListView and therefore the context in the event is related to the item.

Example, see if you can adjust it to your situation:

protected void ListView_ItemDataBound(object sender, ListViewItemEventArgs e)
{
    if (e.Item.ItemType == ListViewItemType.DataItem)
    {
        Label monkeyLabel = (Label)e.Item.FindControl("monkeyLabel");
        bool linkable = (bool)DataBinder.Eval(e.Item.DataItem, "IsLinkable");
        if (linkable)
           monkeyLabel.Text = "monkeys!!!!!! (please be aware there will be no monkeys, this is only for humour purposes)";
    }
}

edited Apr 10 '11 at 14:33

answered Apr 08 '11 at 14:27

Bazzz

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I think the issue is he is embedding a statement into something that expects an expression. – asawyer Apr 08 '11 at 14:44
@asawyer Sounds like a good explanation to me. I haven't really thought about it this way but it makes perfect sense. – Bazzz Apr 10 '11 at 14:29
1

This also applies to the Repeater control. – Bern Nov 22 '13 at 15:42

asawyer · Answer 2 · 2011-04-08T16:53:33.023

15

I'm pretty sure you can do something like the following

(Note I don't have a compiler handy to test the exact syntax)

text = '<%# string.Format("{0}", (bool)Eval("IsLinkable") ? "Monkeys!" : string.Empty) %>'

Yes this is c# and your using vb.net, so you'll need to use vb syntax for a ternary operator.

Edit - was able to throw into into a simple data bind situation, worked like a charm.

edited Apr 08 '11 at 16:53

answered Apr 08 '11 at 14:40

asawyer

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The OP is not using `vb` but `c#` (see tags), so your example is relevant. I think you'll need to start it with `<%#` though, but correct me if I'm wrong. – Bazzz Apr 08 '11 at 16:04
@Bazzz Oh look at that, it is c#. Even better! Also you are correct it should be <%#, i'll update the answer. – asawyer Apr 08 '11 at 16:53

score 8 · Answer 3 · edited Dec 10 '16 at 01:41

8

You can use asp:PlaceHolder and in Visible can put eval. Like as below

   <asp:PlaceHolder ID="plc" runat="server" Visible='<%# Eval("IsLinkable")%>'>
       monkeys!!!!!!
       (please be aware there will be no monkeys, this is only for humour purposes)
   </asp:PlaceHolder>

edited Dec 10 '16 at 01:41

Hadi

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answered Oct 02 '14 at 11:58

Rakesh Angre

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score 6 · Answer 4 · edited Nov 19 '19 at 12:02

6

OMG this took entirely too long to figure out...

<asp:PlaceHolder runat="server" Visible='<%# Eval("formula.type").ToString()=="0" %>'> Content </asp:PlaceHolder>

formula.type is a linked table's int column. Thanks for the other contributions to get my resolution.

edited Nov 19 '19 at 12:02

Chris Mantle

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answered Jul 30 '17 at 02:37

Alec Effrat

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score 4 · Answer 5 · answered Aug 03 '13 at 10:13

4

I know it is a bit late in the day for this answer but for what it is worth here is my solution to the problem:

<%# (bool)Eval("IsLinkable") ? "monkeys!!!!!!" : "" %>

answered Aug 03 '13 at 10:13

oliver

157
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score 4 · Answer 6 · answered Oct 07 '11 at 09:45

If you are having issues getting e.Item.DataItem in Bazzz's answer try

protected void ListView_ItemDataBound(object sender, ListViewItemEventArgs e)
{
    using (ListViewDataItem listViewDataItem = (ListViewDataItem) e.Item)
    {
        if (listViewDataItem != null)
        {
            Label monkeyLabel = (Label)e.Item.FindControl("monkeyLabel");
            bool linkable = (bool)DataBinder.Eval(listViewDataItem , "IsLinkable");
            if (linkable)
               monkeyLabel.Text = "monkeys!!!!!! (please be aware there will be no monkeys, this is only for humour purposes)";
        }
    }
}

score 2 · Answer 7 · answered Jul 22 '14 at 20:01

2

You can create a method to evaluate the value and return the value you want.

<%# IsLinkableABool( Eval("IsLinkable") ) %>

On the code behind you can create the method as follow

protected String IsLinkableABool(String isLinkable)
{
    if (isLinkable == Boolean.TrueString)
    {
         return "monkeys!!!!!! (please be aware...";    
    }
    else
    {
         return String.Empty;
    }
}

answered Jul 22 '14 at 20:01

Oscar

39
3

AWESOME SOLUTION... Sorry for the caps! You saved my day :) – SearchForKnowledge Oct 20 '14 at 15:29

score 1 · Answer 8 · answered Apr 08 '11 at 14:43

Whenever I've needed to handle conditions within a databound control, I use the OnItemDataBound event.

So you could do:

protected void DataBound_ItemDataBoundEvent() {
     bool IsLinkable            = (bool)DataBinder.Eval(e.Item.DataItem, "IsLinkable");  
     if(IsLinkable) {
          //do stuff
     }                                     

}

score 0 · Answer 9 · answered May 25 '17 at 07:05

Putting condition aspx page is not a good idea.also messy. U can do using ternary operator.But I suggest u to use rowdatabound events of grid view. step 1-go to grid view properties.Click on lighting button to list all event. Step 2-give a name on rowdatabound and double click

protected void onrow(object sender, GridViewRowEventArgs e)

   {
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        TableCell statusCell = e.Row.Cells[8];//Means column 9

        if (statusCell.Text == "0")
        {
            statusCell.Text = "No Doc uploaded";

        }
        else if (statusCell.Text == "1")
        {
            statusCell.Text = "Pending";
        }
        else if (statusCell.Text == "2")
        {
            statusCell.Text = "Verified";
        }
    }
}

score 0 · Answer 10 · answered Apr 08 '11 at 14:23

We would need to see the rest of your code, but the error message is giving me a bit of a hint. You can ONLY use Eval when you are inside of a data-bound control. SOmething such as a repeater, datagrid, etc.

If you are outside of a data bound control, you could load the value into a variable on the code-behind and make it public. Then you could use it on the ASPX for conditional processing.

score 0 · Answer 11 · edited Nov 10 '12 at 20:53

For FormView Control refer to this link.

Here is the sample code. My aspx page FormView Control look like below:

<asp:FormView ID="fv" runat="server" Height="16px" Width="832px"  
CellPadding="4" ForeColor="#333333" ondatabound="fv_DataBound"> 
    <ItemTemplate>
        <table>
            <tr>
                <td align="left" colspan="2" style="color:Blue;">
                    <asp:Label ID="lblPYN" runat="server" Text='<%# Eval("PreviousDegreeYN") %>'></asp:Label> 
                </td>
            </tr>
        </table>
    </ItemTemplate>
</asp:FormView>

I am checking the value for <%# eval("PreviousDegreeYN") %>

If my eval("PreviousDegreeYN") == True, I want to display Yes in my label "lblPYN"

protected void fv_DataBound(object sender, EventArgs e)
{
    FormViewRow row = fv.Row;
    //Declaring Variable lblPYN
    Label lblPYN;
    lblPYN = (Label)row.FindControl("lblPYN");
    if (lblPYN.Text == "True")
    {
        lblPYN.ForeColor = Color.Blue;
        lblPYN.Text = "Yes";

    }
    else
    {
        lblPYN.ForeColor = Color.Blue;
        lblPYN.Text = "No";

    }
}

ASP.NET using Bind/Eval in .aspx in If statement

11 Answers11

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