Use of FirstOrDefault() method

Question

3.80/5 (5 votes)

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Hello to everyone and here is my question.

Is there way when I'm using FirstOrDefault method, when there is no data on row, that FirstOrDefault method write my desired text as data in that row?

Sorry for bad explanation..

Okay here it is better:

I have for example this data in my table TEST_TABLE
1. First Person
2. Second Person
3. Third Person

When I'm getting stuff from THIS_TABLE with querry, if is my filter 1 i'll get First Person, if my filter is 2 I'll get Second Person, if 3 i'll get Third Person..
But when my filter reaches 4 I get error that says "nothing there"..
Sooo, when there is no data in row I want to write on that field "NO NAME" or something else..
SOmething like this .FirstOrDefault("THIS IS DEFAULT TEXT IF THERE IS NO DATA"); ?!

I think that now is much clearer to understand..

Posted 3-Aug-12 9:27am

Gabrijel Baban

Updated 3-Aug-12 9:38am

v3

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Comments

Kenneth Haugland 3-Aug-12 15:28pm

I dont understand your question. Do you want to have a new roe pre-filled with information?

Gabrijel Baban 3-Aug-12 15:37pm

Explanation edited..

Kenneth Haugland 3-Aug-12 15:42pm

IUll give you a 5 for the improved question :) (its rare to see)

Sergey Alexandrovich Kryukov 3-Aug-12 15:38pm

I think I understand this (incomplete of course) question well enough to answer, please see.
--SA

Aditya Mangipudi 3-Aug-12 15:29pm

I dont understand the desired text part.

Gabrijel Baban 3-Aug-12 15:37pm

Explanation edited..

Gabrijel Baban 3-Aug-12 16:01pm

Thank you all, I've managed it :)

4 solutions

Solution 1

This method (http://msdn.microsoft.com/en-us/library/bb340482.aspx[^]) is too trivial to discuss it seriously:

C#

if (MyCollection.Count < 1)
   WriteMyDesiredTextAsDataInThatRow(); // :-)
else
   WriteInThatRow(MyCollection[0]);

What you mean by "desired text" or "write in that row" is totally up to you, but Enumerable.FirstOrDefault<tsource></tsource> returns default(TSource) in case of empty source, which may or may not be your "desired text" in your case.

—SA;

Posted 3-Aug-12 9:38am

Sergey Alexandrovich Kryukov

Comments

Gabrijel Baban 3-Aug-12 15:48pm

I don't need to insert anything to my DB.. What I really do is this: I'm taking data from DB and show it in labels that I created in windowsForm.. So, If there is data in DB my labels are filled with it, but when there is no data I'm getting error. So I want to write in that label some message to replace non existing data and continue with code execution. YOur solution is for inserting data in DB, am I right?

Sergey Alexandrovich Kryukov 3-Aug-12 17:00pm

I am not talking about insert. I answer your question about FirstOfDefault. Anything not clear?
--SA

Solution 4

What you need to know about FirstOrDefault and First is most significanly, if First does not find a value, you will get an exception.

In most cases FirstOrDefault will return null if there is no match, thus you do not have to deal with an exception. To find out if the value was not found is to check if the value is null. Value types do not have a null value. If you are doing a Linq query that returns a number and there is nothing found, then the returned value will be zero. If it was not for Value types, then could probably call FirstOrDefault FirstOrNullIfNoResults

Posted 3-Aug-12 11:20am

Clifford Nelson

Solution 2

I dont think FirstOrDefault would help in this case. If i understood correctly, then you can just hardcode it your ELSE part or DEFAULT (is using switch case). Try using Enumeration for these.

Good Luck!!

Posted 3-Aug-12 9:42am

Aditya Mangipudi

Comments

Gabrijel Baban 3-Aug-12 15:48pm

Not really know how to use it..
Is there way to do something like this:

xx.First();
IF(xx ) -- what condition? How to check if it's have data or not?
label.Text=xx;
ELSE
label.Text="MY TEXT";

Or in some way to do with FirstOrDefault

Aditya Mangipudi 3-Aug-12 15:52pm

As Sergey posted above you can do something like this.

if (MyCollection.Count < 1)
MYENUMERATION.NONAME
else
WriteInThatRow(MyCollection[i]);

where [i] is row. Again this is just a algorithm. Try to code it yourself.

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Gabrijel Baban · Accepted Answer · 2012-08-03T10:00:00

Solution 3

Okay, I get it :D

First thing to do when creating linq querry is to use .FirstOrDefault() method

C#

var xx=(from x in y 
        where id=TempID
        select z).FirstOrDefault();

Second thing to do is to check that with if else as I said..

C#

if (xx == null)
  label = "No data";
else 
  label = xx;

:) Here it is and it's working :)

Posted 3-Aug-12 10:00am

Gabrijel Baban

Updated 3-Aug-12 10:03am

v2

Comments

Aditya Mangipudi 3-Aug-12 16:12pm

Good Job.