If dataitem is Null I want to show 0
<asp:Label ID="Label18" Text='<%# Eval("item") %>' runat="server"></asp:Label>
How can I accomplish this?
You can also create a public method on the page then call that from the code-in-front.
e.g. if using C#:
public string ProcessMyDataItem(object myValue)
{
  if (myValue == null)
  {
     return "0 value";
  }
  return myValue.ToString();
}
Then the label in the code-in-front will be something like:
<asp:Label ID="Label18" Text='<%# ProcessMyDataItem(Eval("item")) %>' runat="server"></asp:Label>
Sorry, haven't tested this code so can't guarantee I got the syntax of "<%# ProcessMyDataItem(Eval("item")) %>" entirely correct.
I'm using this for string values:
<%#(String.IsNullOrEmpty(Eval("Data").ToString()) ? "0" : Eval("Data"))%>
You can also use following for nullable values:
<%#(Eval("Data") == null ? "0" : Eval("Data"))%>
Also if you're using .net 4.5 and above I suggest you use strongly typed data binding:
<asp:Repeater runat="server" DataSourceID="odsUsers" ItemType="Entity.User">
    <ItemTemplate>
        <%# Item.Title %>
    </ItemTemplate>
</asp:Repeater>
I use the following for VB.Net:
<%# If(Eval("item").ToString() Is DBNull.Value, "0 value", Eval("item")) %>
It should work as well
Eval("item") == null?"0": Eval("item");
Moreover, you can use (x = Eval("item") ?? 0) in this case.
I don't know ASP.NET very well, but can you use the ternary operator?
http://en.wikipedia.org/wiki/Ternary_operation
Something like: (x=Eval("item")) == Null ? 0 : x
try this code it might be useful -
<%# ((DataBinder.Eval(Container.DataItem,"ImageFilename").ToString()=="") ? "" :"<a
 href="+DataBinder.Eval(Container.DataItem, "link")+"><img
 src='/Images/Products/"+DataBinder.Eval(Container.DataItem,
 "ImageFilename")+"' border='0' /></a>")%>
Used a modified version of Jason's answer:
public string ProcessMyDataItem(object myValue)
{
  if (myValue.ToString().Length < 1)
  {
     return "0 value";
  }
  return myValue.ToString();
}
Try replacing <%# Eval("item") %> with <%# If(Eval("item"), "0 value") %> (or <%# Eval("item") ?? "0 value" %>, when using C#).
Use IIF.
<asp:Label ID="Label18" Text='<%# IIF(Eval("item") Is DBNull.Value,"0", Eval("item") %>' 
runat="server"></asp:Label>
I have tried this code and it works well for both null and empty situations :
'<%# (Eval("item")=="" || Eval("item")==null) ? "0" : Eval("item")%>'
来源:https://stackoverflow.com/questions/1979806/using-evalitem-handling-null-value-and-showing-0-against