Need string if har row to show value, else to be ----

Question

1.00/5 (1 vote)

See more:

Need string if har row to show value, else to be ----

I try this
What I wrong?

What I have tried:

C#

string redni_broj = "";
           using (SqlConnection openCon8 = new SqlConnection(Con))
           {
               SqlDataReader reader8;
               SqlCommand cmd8 = new SqlCommand();
               cmd8.CommandText = "select FORMAT(redni_broj, '00000') from mp_faktura_lista where id=" + id_fakture;
               cmd8.Connection = openCon8;
               openCon8.Open();
               reader8 = cmd8.ExecuteReader();
               if (reader8.HasRows)
               {
                   while (reader8.Read())
                   {
                       redni_broj = reader8[0].ToString();
                   }
               }
               else
               {
                   redni_broj = "-----";
               }
               openCon8.Close();
           }

Posted 2-Nov-19 2:25am

Goran Bibic

Updated 2-Nov-19 3:56am

Add a Solution

Comments

MadMyche 2-Nov-19 8:47am

Please update your question using the Improve Question widget to add in:
1. What data type is redni_broj? What is the actual value?
2. What does this function currently return? Are there errors?

Goran Bibic 2-Nov-19 8:59am

1. What data type is redni_broj? int
What is the actual value? acutal is null
2. What does this function currently return? curently if is null (empty), if have value exmp 1 (write 00001)
Are there errors? No have errors

2 solutions

Solution 2

First and Foremost
This code is susceptible to SQL Injection. You should NEVER EVER put together a query by splicing user input in.
The proper method to add in the values is to use Parameters. Here is how this would look for your command, with some code reorganization as well

C#

string qry = "SELECT Format(redni_broj, '00000') FROM mp_faktura_lista WHERE id= @id";
SqlCommand cmd8 = new SqlCommand(qry, openCon8);
cmd8.Parameters.AddWithValue("@id", id_fakture);

SqlDataReader and ExecuteReader
Your code is designed to return one and only one value; there is no reason to utilize this method, rather you should be using the ExecuteScalar() method

C#

openCon8.Open();
var result = cmd8.ExecuteScalar();
if (result != null) { redni_broj = result.ToString(); }
else { redni_broj = "-----"; }
openCon8.Close();

My personal preferences
I would recommend not to use the Format() function in SQL. The reason is that the actual format that is being shown is a Presentation Layer concern and should not be in the business logic. Another valid reason is that sting functions within SQL is not as efficient as doing in application code.
What I would do is just to return the value as is (or null) and use application code for the formatting of it. You are already calling the ToSting() method, so you may as well utilize its overload method.

References:
SqlCommand.ExecuteScalar Method (System.Data.SqlClient) | Microsoft Docs[^]

Posted 2-Nov-19 3:56am

MadMyche

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)

OriginalGriff · Accepted Answer · 2019-11-02T02:45:00

First off, don't do it like that: Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Always use Parameterized queries instead.

When you concatenate strings, you cause problems because SQL receives commands like:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'

The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;--'

Which SQL sees as three separate commands:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';

A perfectly valid SELECT

SQL

DROP TABLE MyTable;

A perfectly valid "delete the table" command

SQL

--'

And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.

So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?

Second, you don't need a while - your code will just set it to the last value in the reader, so you are probably better off withj an if instead:

C#

reader8 = cmd8.ExecuteReader();
if (reader8.Read())
{
   redni_broj = reader8[0].ToString();
}
else
{
   redni_broj = "-----";
}

Or even just

C#

reader8 = cmd8.ExecuteReader();
redni_broj = reader8.Read() ? reader8[0].ToString() : "-----";