Solved

DBNULL

Posted on 2011-09-28
5
372 Views
Last Modified: 2012-05-12
Hi,

I keep getting the error message

Unable to cast object of type 'System.DBNull' to type 'System.String'.

when i do the following code.
if (e.Row.Cells[j] != null && ((string)e.Row.Cells[j].Data.DataItem).Contains("text"))

I think its to do with this part ((string)e.Row.Cells[j].Data.DataItem).Contains("text"))

Can someone please help.

Thanks
0
Comment
Question by:cjJosephj
[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
5 Comments
 
LVL 23

Accepted Solution

by:
wdosanjos earned 125 total points
ID: 36719730
Please try the following:

if (e.Row.Cells[j] != null && e.Row.Cells[j].Data.DataItem is string && ((string)e.Row.Cells[j].Data.DataItem).Contains("text"))
0
 
LVL 4

Expert Comment

by:theHollow
ID: 36719768
Hello
e.Row.Cells[j] will never be "null".
But it might be "System.DBNull", which is a "database null value".

You can try the following:

if ((e.Row.Cells[j] != DBNull.Value) && e.Row.Cells[j].Data.DataItem.ToString().Contains("text"))
{
    // do stuff
}

Open in new window


Hope it helps :-)
0
 
LVL 6

Expert Comment

by:effes
ID: 36719875
Just to add my two cents: I think it should be either
if (!(e.Row.Cells[j].Value is DBNull) && ((string)e.Row.Cells[j].Data.DataItem).Contains("text"))

Open in new window

or
if (e.Row.Cells[j].Value != DBNull.Value && ((string)e.Row.Cells[j].Data.DataItem).Contains("text"))

Open in new window

.
0
 
LVL 4

Expert Comment

by:theHollow
ID: 36720073
Hi
To specify my answer further:
Because you use "&&" operand (which exuals the VB.NET "AndAlso"), the second check will be igonred if the first was "true".

Therefore, there is nothing wrong with the second check in the "if".
However...e.Row.Cells[j] is not "null". It is System.DBNull. So it crash on the second test.

So in your if-statement, the symptom is the second check. The real problem is the first check, which should not check with "null", but "DBNull.Value" :-)
0
 

Author Comment

by:cjJosephj
ID: 36813662
Thank you all for your quick replies


0

Featured Post

Online Training Solution

Drastically shorten your training time with WalkMe's advanced online training solution that Guides your trainees to action. Forget about retraining and skyrocket knowledge retention rates.

Question has a verified solution.

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

More often than not, we developers are confronted with a need: a need to make some kind of magic happen via code. Whether it is for a client, for the boss, or for our own personal projects, the need must be satisfied. Most of the time, the Framework…
Calculating holidays and working days is a function that is often needed yet it is not one found within the Framework. This article presents one approach to building a working-day calculator for use in .NET.
With Secure Portal Encryption, the recipient is sent a link to their email address directing them to the email laundry delivery page. From there, the recipient will be required to enter a user name and password to enter the page. Once the recipient …
Finding and deleting duplicate (picture) files can be a time consuming task. My wife and I, our three kids and their families all share one dilemma: Managing our pictures. Between desktops, laptops, phones, tablets, and cameras; over the last decade…

738 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