Calculated column in gridview fails if value is null.

Try something like this

If you still need the control:

<% If( IsNull(Eval("StartTime")) or IsNull(Eval("StoreArrival")) or IsNull(Eval("StoreDepart")) or IsNull(Eval("EndofDay")) ){ %>
  <asp:Label ID="Label5" Text = '' runat="Server" />
<% }else{ %>
  <asp:Label ID="Label5" Text = '<%#Get_Travel_Hours(Eval("StartTime"), Eval("StoreArrival"), Eval("StoreDepart"), Eval("EndofDay")) %>' runat="Server" />
<% } %>

If you don't need it at all:

<% If( Not (IsNull(Eval("StartTime")) or IsNull(Eval("StoreArrival")) or IsNull(Eval("StoreDepart")) or IsNull(Eval("EndofDay"))) ){ %>
  <asp:Label ID="Label5" Text = '' runat="Server" />
<% }else{ %>
  <asp:Label ID="Label5" Text = '<%#Get_Travel_Hours(Eval("StartTime"), Eval("StoreArrival"), Eval("StoreDepart"), Eval("EndofDay")) %>' runat="Server" />
<% } %>

Sorry Mistake there

If you don't need it at all:

<% If( Not (IsNull(Eval("StartTime")) or IsNull(Eval("StoreArrival")) or IsNull(Eval("StoreDepart")) or IsNull(Eval("EndofDay"))) ){ %>
  <asp:Label ID="Label5" Text = '<%#Get_Travel_Hours(Eval("StartTime"), Eval("StoreArrival"), Eval("StoreDepart"), Eval("EndofDay")) %>' runat="Server" />
<% } %>

I get an "ISNULL" is not declared error.

Try

<% If( Not (Eval("StartTime") is null or Eval("StoreArrival") is null or Eval("StoreDepart") is null or Eval("EndofDay") is null) ){ %>
  <asp:Label ID="Label5" Text = '<%#Get_Travel_Hours(Eval("StartTime"), Eval("StoreArrival"), Eval("StoreDepart"), Eval("EndofDay")) %>' runat="Server" />
<% } %>

I think it depends on your page language (VB, C#)

I am using VB.  ISNULL is no longer supported.  i changed it to the following.

 <% If (IsDBNull("StartTime") Or IsDBNull("StoreArrival") Or IsDBNull("StoreDepart") Or IsDBNull("EndofDay")) Then%>
                    <asp:Label ID="Label5" Text = '' runat="Server" />
                    <% Else%>
                    <asp:Label ID="Label6" Text = 'all empty' runat="Server" />
             <%--       <asp:Label Text = '<%#Get_Travel_Hours(Eval("StartTime"), Eval("StoreArrival"), Eval("StoreDepart"), Eval("EndofDay")) %>' runat="Server" />--%>
                    <%  End If%>

It seems to work but all rows in datagrid are evaulating to "all empty" even if all 4 fields have a time in them.

I removed the eval due to an error regarding binding.  The above will not evaluate coreectly because I am just using a string.  I need to find a better way.

The way you did it, it goes to the TRUE part if any of the 4 field is empty and if none of them are empty it outputs 'all empty'.

Do you mean that every row displays 'all empty', which is wrong because you have some empty?

Something else you could do is test the parameters when you are inside the function Get_Travel_Hours and return '' if one of them is empty.

A line like  <% If (Eval("StartTime") < "") Then%>

Produces the error

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

I tried to test them inside the function, but it would not pass them if they were empty, I would get a casting error.

Can I test the column of the gridview to see if it's empty?

I need to check them before I call the function, mainly because if they are empty they fail before and after the function is called.

<asp:label runat="server"
     Text='<%# DataBinder.Eval(Container.DataItem,
          "StartTime") %>'
   />

This will place empty string in label, but when I try to use it inside an if statement the Container becomes unrecognized.

I solved it another way, but thanks for the help and sugestions that lead to the solution.