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using Eval in vb.net

Answer 1

A:

The issue is that you are using C# features in a VB.NET web application.

The null keyword and the ?: and == operators are C# constructs

In VB.NET, null is Nothing, == is IS and ?: is the IIf function.

Oded 2010-05-08 11:50:25

thanx for ur answer Oded ....but still i have problem ..when i chang the code that u put it its give this Error :Compiler Error Message: BC30456: 'PAGE_TITLE_AR' is not a member of 'Char'.i wrote my code like this :`<asp:Label ID="Label1" runat="server" Text='<%#Eval("Pages") is Nothing IIf ((ReportsOfficesModel.Pages)(Eval("Pages"))).PAGE_TITLE_AR %>'></asp:Label>`

Bin_Zain 2010-05-08 12:04:02

The `IIf` function is not suitable here, since it always evaluates both the True and the False clause. Thus, accessing `Eval("PAG_PAGES")`'s member will result in a NullReferenceException, if `Eval("PAG_PAGES")` is Nothing. The `If` operator solves this problem.

Heinzi 2010-05-08 12:32:33

Answer 2

A:

<%# If(Eval("PAG_PAGES") Is Nothing, 
        "", 
        DirectCast(Eval("PAG_PAGES"), PostAgenciesModel.PAG_PAGES).PAGE_TITLE_AR) %>

Elaborating on what Oded wrote:

expr == null  --->  expr Is Nothing
a ? b : c     --->  If(a, b, c)
(Type)expr    --->  DirectCast(expr, Type)

Heinzi 2010-05-08 12:26:20

hii....thanx for the answers guys.....but still i have problem ...the messege erroe shows : ' BC30007: Reference required to assembly 'System.Data.Entity, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' containing the base class 'System.Data.Objects.DataClasses.EntityObject'. Add one to your project.'i do add refernce in my project 'System.Data.Entity' but i don't know what is the problem

Bin_Zain 2010-05-09 07:12:02

@Bin: This is a different problem (related to the entity framework, not to C# -> VB.NET); you should open a second question for that (and tag it with `entity-framework`).

Heinzi 2010-05-09 09:36:20

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