Datareader don't fetch data from database

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I have a function as IEnumerable that fetch all data from a table in database by stored procdure using executereader but return null In the event that table have any record

What I have tried:

C#

public IEnumerable<adress_> GetAllAdress_()
        {
            try
            {
                List<adress_> lstadress_ = new List<adress_>();

                using (SqlConnection con = new SqlConnection(connectionString))
                {
                    SqlCommand cmd = new SqlCommand("spGetAllAdress_s", con);
                    cmd.CommandType = CommandType.StoredProcedure;

                    con.Open();
                    SqlDataReader rdr = cmd.ExecuteReader();

					while (rdr.Read())
                    {

						Adress_ adress_ = new Adress_();

						adress_.adressId = Convert.ToInt32(rdr["adressId"]);
                         adress_.persianAdress.ToString();
                         adress_.inhabitAdress.ToString();
                         adress_.adressInforigen.ToString();
                         adress_.branch.ToString();
                         adress_.postCode.ToString();
                         adress_.startDate.ToString();
                         adress_.endDate.ToString();


                        lstadress_.Add(adress_);
                    }
                    con.Close();
                }
                return lstadress_;
            }
            catch
            {
				return null;
            }
        }

Posted 7-Feb-21 7:35am

Ali Jafarinezhad

Updated 7-Feb-21 8:13am

RickZeeland

v2

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Luc Pattyn · Accepted Answer · 2021-02-07T07:41:00

Solution 1

A try-catch block is intended to catch an Exception, i.e. an object that describes what went wrong. You seem not interested in it.

:(

Posted 7-Feb-21 7:41am

Luc Pattyn

Comments

Ali Jafarinezhad 7-Feb-21 13:57pm

Your answer was irrelevant to my question

OriginalGriff · Accepted Answer · 2021-02-07T08:13:00

Solution 2

Quote:
Your answer was irrelevant to my question

No, it wasn't. Luc was absolutely spot-on, if a little terse - he probably assumed you knew what you were doing and would understand what he said.

Allow me to expand on his answer:
When you use a try...catch in your code and ignore the actual exception you throw away all the information that would tell you exactly what your problem is. You have a try block around the whole DB operation, but your catch block collects all exception types and discards them in favour of returning a null value.
So if your connection string is wrong - you return null.
If your SP doesn't exist - you return null.
If your SP fails - you return null.
If there is no column of that name returned - you return null.
If ... you get the idea.

If you aren't going to handle the error yourself, don't use a try...catch block. Returning a null error code is old-school: the modern thinking is that if you can't deal with it, let the exception filter up to a level that can. That way a multi-layer app can find a problem is -say- the data layer, and "bubble the exception up" through the Business layer to the Presentation layer which is the only one that can let the user know there was a problem - and still access the Exception object to tell him what the problem was!

With your method, your null return tells the calling method that something went wrong, but gives nobody any idea what it might have been!

Luc's answer wasn't irrelevant - you just didn't understand it.

Posted 7-Feb-21 8:13am

OriginalGriff

Comments

Ali Jafarinezhad 7-Feb-21 14:27pm

Yes, you are right. My answer was a bit hasty. I apologize to Luc for this. I found the answer. In fact, I forgot to enter the second part of the phrase and I should have written like this
adress_.inhabitAdress = rdr ["inhabitAdress" ] .ToString ()
I wrote in a hurry and I think I wrote in a hurry and I think I should use it better from try-catch, thank you

Luc Pattyn 7-Feb-21 14:49pm

+5good cop bad cop routine often works wonders...

:)

OriginalGriff 7-Feb-21 15:38pm

:DSo who's the bad cop?

Luc Pattyn 7-Feb-21 15:50pm

I dunno.
The one that encourages reflection?
The one that interrupts and spoon feeds?
The one that provokes a non-stock reply?

OriginalGriff 7-Feb-21 16:15pm

Let's just blame Harry Callahan and not worry about it! ;D

Luc Pattyn 7-Feb-21 16:18pm

That's Tom Barnaby's twin brother, isn't he?

OriginalGriff 7-Feb-21 16:54pm

:DI'm always amazed anyone moves to Midsomer Norton: Population about 60, with 6 murdered every week ...

Off topic: it's good to see your name appearing on the "Top Experts" list - your wisdom has been sorely missed!

Luc Pattyn 7-Feb-21 17:18pm

There's only a few episodes per series, and they keep importing ex-wives, forgotten siblings, tourists, fresh nobility, strange cultists, and more potential victims, so Midsomer is doing well actually.

Top Expert? that is hard to believe, I only answer a few questions, I tend to pick the ones that I know something about AND show some potential. Which doesn't add up much. So I was quite surprised a few weeks ago when I received an email announcing another MVPship... Things must go really badly.

But you Sir, you're a rock.

:)

OriginalGriff 7-Feb-21 17:24pm

Check the QA page: https://www.codeproject.com/script/Answers/List.aspx?tab=unanswered
Right hand side, you're in second place for today.
Ignore me being at the top, that's always a misprint. I think I send the Hamsters too many fermented sunflower seeds ... :laugh:

I know what you mean though, there are too many posters that just aren't interested in getting an answer - they just want code they can hand in. :sigh:

Luc Pattyn 7-Feb-21 17:33pm

Sunflower seeds? Did you run out of kopi luwak? And they didn't notice?

OriginalGriff 7-Feb-21 17:43pm

Hah! Mere sunflower seeds run away screaming in terror when they see Chris's coffee machine!
https://www.codeproject.com/Messages/5775509/Re-Bean-to-cup-machines-Coffee-of-course

Datareader don't fetch data from database

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