Optimizing a for loop in C#

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Hi all,

I have a for loop that I wish to optimize, someone can help me or give me some tricks to optimize

string sql1 = "select * from (select distinct left(start_bin_value,6) from sys_mast_inter_bin_table mast join cht_card_brand cb on mast.card_brand = cb.index_field join cht_country ctry on mast.bin_country = ctry.index_field join cht_service_type st on mast.service_type = st.index_field where cb.card_brand = '" + this.Card_brand + "' and ctry.client_country = '" + this.Bin_country + "' and st.service_type = '" + this.Service_type + "' ) where rownum <= " + this.TestCases + " order by dbms_random.value";

                       OleDbCommand command1 = new OleDbCommand(sql1, this.Connection);
                       OleDbDataReader reader1 = command1.ExecuteReader();
                       LuhnCheck lc = new LuhnCheck();

                       while (reader1.Read())
                       {
                           string result = lc.generate(reader1[0].ToString(), Convert.ToInt32(txtChangeLength.Text));
                           txtRandCardNumbers.Text += result + Environment.NewLine;
                       }
                       int rows = this.TestCases;
                       string[] textCardNumber = new string[rows];
                       StringReader readingCardNumber = new System.IO.StringReader(txtRandCardNumbers.Text);
                       int numberofrows = txtRandCardNumbers.Lines.Count() - 1;
                       if (reader1.Read() == false && numberofrows < this.TestCases)
                       {
                           int f = 0;
                           int loop = this.TestCases - txtRandCardNumbers.Lines.Count();

                           for (int cx = 0; cx <= loop; cx++)
                           {
                               textCardNumber[cx] = readingCardNumber.ReadLine();
                               if (textCardNumber[cx] is null)
                               {
                                   textCardNumber[cx] = textCardNumber[f + 0];
                                   f++;
                               }
                               txtRandCardNumbers.Text += textCardNumber[cx] + Environment.NewLine;

                           }
                       }
                       reader1.Close();
                   }

What I have tried:

I tried to surf the internet and I found out about parallel array but I don't know how I can do it.

Posted 26-Sep-17 0:20am

Joe Doe234

Updated 26-Sep-17 13:00pm

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Comments

Richard Deeming 26-Sep-17 15:00pm

Your code is vulnerable to SQL Injection[^]. NEVER use string concatenation to build a SQL query. ALWAYS use a parameterized query.

Everything you wanted to know about SQL injection (but were afraid to ask) | Troy Hunt[^]
How can I explain SQL injection without technical jargon? | Information Security Stack Exchange[^]
Query Parameterization Cheat Sheet | OWASP[^]

2 solutions

Solution 2

C#

string sql1 = "select * from (select distinct left(start_bin_value,6) from sys_mast_inter_bin_table mast join cht_card_brand cb on mast.card_brand = cb.index_field join cht_country ctry on mast.bin_country = ctry.index_field join cht_service_type st on mast.service_type = st.index_field where cb.card_brand = '" + this.Card_brand + "' and ctry.client_country = '" + this.Bin_country + "' and st.service_type = '" + this.Service_type + "' ) where rownum <= " + this.TestCases + " order by dbms_random.value";

Not a solution to your question, but another problem you have.
Never build an SQL query by concatenating strings. Sooner or later, you will do it with user inputs, and this opens door to a vulnerability named "SQL injection", it is dangerous for your database and error prone.
A single quote in a name and your program crash. If a user input a name like "Brian O'Conner" can crash your app, it is an SQL injection vulnerability, and the crash is the least of the problems, a malicious user input and it is promoted to SQL commands with all credentials.
SQL injection - Wikipedia[^]
SQL Injection[^]
SQL Injection Attacks by Example[^]
PHP: SQL Injection - Manual[^]
SQL Injection Prevention Cheat Sheet - OWASP[^]

Posted 26-Sep-17 13:00pm

Patrice T

Comments

Joe Doe234 27-Sep-17 3:40am

and what can I do instead of ex: this.card_brand?

PS: These are all combo boxes and the 2 textboxes I have only accepts numbers.

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Graeme_Grant · Accepted Answer · 2017-09-26T00:29:00

Solution 1

C#

txtRandCardNumbers.Text += textCardNumber[cx] + Environment.NewLine;

I would use StringBuilder[^]

C#

var sb = new StringBuilder;

for (int cx = 0; cx <= loop; cx++)
{
    ...
    sb.AppendLine(textCardNumber[cx]);
    ...
}

txtRandCardNumbers.Text = sb.ToString();

Posted 26-Sep-17 0:29am

Graeme_Grant

Comments

Joe Doe234 26-Sep-17 6:31am

thanks graeme , there is something else that i can change ? i just need to learn optimization