Run a callback on bound fields of a Gridview

Question

I want to process a field retrieved from the database for a Gridview to check to see if the information in it is a hyperlink. If it is, I want to generate a link from it, otherwise just leave it as raw text. At the moment the field in the Gridview looks like:

    <asp:TemplateField HeaderText="Reference">
        <EditItemTemplate>
            <asp:TextBox ID="txtReference" runat="server" Text='<%# Bind("Reference") %>'></asp:TextBox>
        </EditItemTemplate>
        <ItemTemplate>
            <asp:Label ID="Label3" runat="server" Text='<%# Bind("Reference") %>'></asp:Label>
        </ItemTemplate>
    </asp:TemplateField>

I tried modifying what's in the 'Text' attribute of the ItemTemplate but no matter what I put in I get errors on pageload. How can I dynamically modify what's sent to the browser based on the specific info bound in this field?

Thanks a lot!

Answer 1

I fixed this by using both a Label and a HyperLink in my TemplateField, showing the HyperLink (and hiding the Label) if the bound text qualifies as a proper URL.

The following ASP.NET sets up the potential HTML to output:

ASP.NET

<asp:TemplateField HeaderText="Reference"> 
    <ItemTemplate>
                <asp:Label ID="lblReference" runat="server" Visible='<%# !isTextHyperlink(Eval("Reference")) %>' Text='<%# Bind("Reference") %>'/>
                <asp:HyperLink ID="hlReference" runat="server" Visible='<%# isTextHyperlink(Eval("Reference")) %>' Text='<%# Bind("Reference") %>' NavigateUrl='<%# Bind("Reference") %>'/>
    </ItemTemplate> 
</asp:TemplateField> 

I added a function in the pages 'codebehind' like this:

C#

protected bool isTextHyperlink(object refobj)
{
    string refstring = refobj.ToString();
    try
    {
        Uri uri = new Uri(refstring);
        return Uri.CheckSchemeName(uri.Scheme);
    }
    catch
    {
        // not a valid uri (that Uri can construct with)
        return false;
    }
}

Many thanks to Brissles for the suggestion.

Answer 2

You can use the GridView.OnRowDataBound method like

protected virtual void yourGV_OnRowDataBound(object sender, gridViewRowEventArgs e)
{
   GridViewRow row = e.Row 
}

inside that you can access the controls in the row with FindControl for example.

Answer 3

You could use both a Label and a HyperLink in your TemplateField and show the HyperLink (and hide the Label) if the bound text qualifies as a proper URL. You can do this using a codebehind function that returns a bool to the Visible property, something like this:

ASP.NET

<asp:TemplateField HeaderText="Reference"> 
    <ItemTemplate> 
        <asp:Label ID="lbl" runat="server" Visible='<%# IsTextHyperlink(Eval("Reference")) %>' Text='<%# Bind("Reference") %>'/>
        <asp:HyperLink ID="hl" runat="server" Visible='<%# !IsTextHyperlink(Eval("Reference")) %>' NavigateUrl='<%# Bind("Reference") %>'/>
    </ItemTemplate> 
</asp:TemplateField> 

C#

protected bool IsTextHyperlink(object text)
{
    bool IsHyperLink = false;
    ...
    // check if text qualifies as hyperlink
    ...
    return IsHyperLink ; 
}

Note using type object for the IsHyperLink function parameter, as Eval() returns an object, just cast it to a String.

You'd want to also format your Text property of your HyperLink to something meaningful.