?
Solved

Check for null value in dataset before assignment

Posted on 2007-11-25
8
Medium Priority
?
707 Views
Last Modified: 2008-02-01
Hello, I'm trying to check for a null value before populating an imageUrl for a hyperlinks that I'm adding to a calendar control. How can this be accomplished?

I'm getting the following error:
Conversion from type 'DBNull' to type 'String' is not valid.

Here is my code:

 If Not dsEvents Is Nothing Then
            For Each dr As DataRow In dsEvents.Tables(0).Rows
                nextDate = CType(dr("Date"), DateTime)
                If nextDate = e.Day.Date Then
                    Dim Id As String = CType(dr("Id"), String)
                    Dim hl As New HyperLink
                    Dim lc As New LiteralControl
                    lc.Text = "</BR>"


                    If IsDBNull(dsEvents.Tables(0).Rows(0).Item("ImageURL")) Then
                        hl.ImageUrl = ""
                    Else
                        hl.ImageUrl = ("EventGraphics/" & CType(dr("ImageURL"), String))
                    End If

                    'this works if all the events added contain imageURL
                    'hl.ImageUrl = ("EventGraphics/" & CType(dr("ImageURL"), String))

                    hl.NavigateUrl = ("DisplayEvent.aspx?ID=" & Id)
                    hl.Text = CType(dr("Title"), String)
                    e.Cell.Controls.Add(lc)
                    e.Cell.Controls.Add(hl)
                    e.Cell.Controls.Add(lc)
                End If
            Next
        End If
0
Comment
Question by:gogetsome
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 4
8 Comments
 
LVL 143

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 20345653
on which line does the error get raised?
0
 

Author Comment

by:gogetsome
ID: 20345674
     hl.ImageUrl = ("EventGraphics/" & CType(dr("ImageURL"), String))
0
 
LVL 143

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 20345678
what about this:

      If (dsEvents.Tables(0).Rows(0).Item("ImageURL") == DBNull.Value) Then
                        hl.ImageUrl = ""
                    Else
                        hl.ImageUrl = ("EventGraphics/" & CType(dr("ImageURL"), String))
                    End If
0
Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 

Author Comment

by:gogetsome
ID: 20345687
how do you convert c# == to vb?
0
 
LVL 143

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 20345691
sorry, my fault ... I am used to C# :)


      If (dsEvents.Tables(0).Rows(0).Item("ImageURL") IS DBNull.Value) Then
                        hl.ImageUrl = ""
                    Else
                        hl.ImageUrl = ("EventGraphics/" & CType(dr("ImageURL"), String))
                    End If
0
 

Author Comment

by:gogetsome
ID: 20345705
Same error.
Some more info. Some of the events have imageURL and some do not.
0
 
LVL 143

Accepted Solution

by:
Guy Hengel [angelIII / a3] earned 2000 total points
ID: 20345754
any better with this

      If (dr("ImageURL") is DBNull.Value) Then
                        hl.ImageUrl = ""
                    Else
                        hl.ImageUrl = ("EventGraphics/" & CType(dr("ImageURL"), String))
                    End If
0
 

Author Comment

by:gogetsome
ID: 20345760
Success!
Thank you AngelIII!
0

Featured Post

Free Tool: SSL Checker

Scans your site and returns information about your SSL implementation and certificate. Helpful for debugging and validating your SSL configuration.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

I have developed many web applications with asp & asp.net and to add and use a dropdownlist was always a very simple task, but with the new asp.net, setting the value is a bit tricky and its not similar to the old traditional method. So in this a…
The article shows the basic steps of integrating an HTML theme template into an ASP.NET MVC project
Michael from AdRem Software explains how to view the most utilized and worst performing nodes in your network, by accessing the Top Charts view in NetCrunch network monitor (https://www.adremsoft.com/). Top Charts is a view in which you can set seve…
Add bar graphs to Access queries using Unicode block characters. Graphs appear on every record in the color you want. Give life to numbers. Hopes this gives you ideas on visualizing your data in new ways ~ Create a calculated field in a query: …
Suggested Courses

752 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question