Filter in Data table using Linq

Question

0.00/5 (No votes)

See more:

Hi All,
I am using this linq to filter rows from data table.

C#

var result = from myRow in dtInventory.AsEnumerable()
 where myRow.Field<string>("Description").StartsWith(letters[0].ToString(), StringComparison.OrdinalIgnoreCase)
select myRow;

when the dtInventory is filled from a SQL table the Query works fine. but when I fill data table by SQL view the Query Throw exception like

"Object reference not set to an instance of an object"

How to resolve the issue??

Regards,
Palraj M.

Posted 25-Jul-13 2:33am

palraj001

Add a Solution

Comments

Alexander Dymshyts 25-Jul-13 8:41am

may be dtInventory is null? Check in debug where you get this error

palraj001 25-Jul-13 9:12am

no dtinventory is not null. it has rows

Kuthuparakkal 25-Jul-13 9:32am

What's this "letters[0].ToString()" ? Replace this with some letter may reveal the issue

palraj001 25-Jul-13 9:51am

sorry.letters is an array . assume any letter for E.g letters[0] ="H"

Kuthuparakkal 25-Jul-13 10:50am

Check the spelling for "Description" in your datatable against the Linq written

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Keith Barrow · Answer 1 · 2013-07-25T05:51:00

We need to do some basic breaking down of the problem: Declare a temporary variable

C#

var foo = from myRow in dtInventory.AsEnumerable() select myRow;

Put on a breakpoint on the above and execute, if foo has rows then you've a different problem so move on. Relying on the table having data is no good. Though I doubt this is your problem, you just get a null or empty value in result
Step 2 is to replace letters[0].ToString() with *any* letter, e.g. "a" (as per Kuthuparakkal suggestion). If you don't get the exception, your array is null at the very least.

If you do get an exception then the problem is myRow.Field<string>("Description") is returning null. You've then got two immediate culprits to investigate: either your field name doesn't match (case sensitive?) or the field itself allows null (loop over the unfiltered results and get each value in turn to see).

If all this fails to diagnose your problem, the only other thing that leaps out is the dtInventory.AsEnumerable(), if this causes myRow to lose the it's column information/context, the .Field<t></t> won't work. This is very unlikely (I've not used this method) given that your code builds, but you could try re-removing the where clause and looping through the unfiltered results, inspecting each DataRow object in turn.