Problem with Substring() - ArgumentOutOfRangeException

Question

I have a repeater that displays data from my Projects table. There are projectId, name and description. I use Substring(1, 240) on description. But sometimes the string is shorter than 240, so I get ArgumentOutOfRangeException. Can you tell me how to display the whole text if I get the exception. This is my code.

    <asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" runat="server"> <asp:Panel ID="pnlDisplayProjects" runat="server" Visible="true">     <center><h2><b>Проекти</b></h2></center>         <asp:Repeater ID="rptrProjects" runat="server">             <HeaderTemplate>                 <table border="1" cellpadding="2" cellspacing="2" align="center" width="80%" style="background-color:#F7F6F3;">             </HeaderTemplate>             <ItemTemplate>                 <tr>                     <td align="left" style="width:40px">                         <asp:Label ID="LblProjectId" runat="server" Text='<%# Eval("ProjectID") %>' />                     </td>                     <td align="center">                         <asp:Label ID="LblName" runat="server" Text='<%# Eval("Name") %>' />                     </td>                 </tr>                 <tr>                     <td colspan="2">                         <asp:Label ID="LblDescription" runat="server" Text='<%# Eval("Description").ToString().Substring(1, 240) + "..." %>'/>                         <asp:HyperLink ID="HlMore" runat="server" NavigateUrl='<%#"~/Project/ViewProject.aspx?projectId=" + Eval("ProjectID") %>' Text="More" />                     </td>                 </tr>             </ItemTemplate>             <FooterTemplate>                 </table>             </FooterTemplate>         </asp:Repeater> </asp:Panel> 

 protected override void OnPreRender(EventArgs e)     {         var table = Projects.GetTableWithProjects();          if (table.Rows.Count > 0)         {             rptrProjects.DataSource = table;             rptrProjects.DataBind();         }         else         {             pnlDisplayProjects.Visible = false;             Master.PrintMessage("There are no projects.");         }     } 

Answer 1

I would suggest you write a separate extension method if you're using .NET 3.5. Something like this:

public static string SafeSubstring(this string text, int start, int length) {     return text.Length <= start ? ""         : text.Length - start <= length ? text.Substring(start)         : text.Substring(start, length); } 

Basically that's a version of Substring which will never throw an exception unless start or length is negative (in which case I don't know what it could sensibly return).

You'd call it like this:

Eval("Description").ToString().SafeSubstring(1, 240) + "..." 

The downside of this is that it will include the ellipsis (...) even if it's not actually truncated the string at all...