Unable to return string from while function

Question

I'm trying to parse data from MariaDB MySQL database, but I have a problem when I try to return CODE. The public static string given below works perfectly, I just want to use parsed data in another class, but whenever the code passes while (rdr.Read()) function, string OTP just dissapears.

I've also tried to move return CODE part outside of the while function braces, but then I'm getting the following error:

"The name 'CODE' does not exist in the current context".

My code:

public static string TESTCODE()
{
    string connStr = "server=XX.XX.XX.XX;user=username;database=dbname;password=password;";
    MySqlConnection conn = new MySqlConnection(connStr);
    conn.Open();

    string query = "Select * from testbase where name='George' and lastname='Brown' order by number desc limit 1";

    MySqlCommand cmd = new MySqlCommand(query, conn);

    using (MySqlDataReader rdr = cmd.ExecuteReader())
    {
        while (rdr.Read())
        {
            string result= rdr.GetString(0);
            string CODE;
            CODE = Regex.Match(result, @"\d+").Value;
            return CODE ;
        }
    }

    return null;
}

Thank you in advance.

On which line do you get the error message from the above code? — Steve
– Steve, Commented Nov 22, 2019 at 8:50
Hi Steve. I don't get error on the code given above. All I want to do is to use string CODE in another class, but whenever the code passes WHILE loop, string CODE is not returned, it just dissapears :( — Shako
– Shako, Commented Nov 22, 2019 at 8:57
You are returning it, so its value doesn't disappear, you just need to get the return value from TESTCODE and assign to another local variable. Like string ANewCODE = TESTCODE(); if(!string.IsNullOrEmpty(ANewCode)) {.....} — Steve
– Steve, Commented Nov 22, 2019 at 9:07
By the way, if the compiler gives you an error, it tells you also where the error happens. If you don't post the code where do you have the error then your questions fills exactly the close reason No minimal reproducible example given — Steve
– Steve, Commented Nov 22, 2019 at 9:10

Christopher · Accepted Answer · 2019-11-22 09:04:20Z

0

SharpLab has no support for the SQL Classes, but those should not mater anyway. I punched this code into SharpLab and it compiles, aside from the expected warning (unreachable return null):

using System;

public class C {
    public void M() {
    }

    public static string TESTCODE()
    {
        while(true){
          string CODE;
          CODE = "not a null";
          return CODE ;
        }

        return null;
    }
}

That leaves only one conclusion: This is not the line causing the issue.

Something else has tripped up the compiler. And it tripped it up so badly, it can not even tell you where the issue is anymore. Please fix all the other issues in your code.

edited Nov 22, 2019 at 9:04

answered Nov 22, 2019 at 8:57

Christopher

9,8442 gold badges19 silver badges31 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Bart · Accepted Answer · 2019-11-22 08:52:20Z

-1

You should define string CODE; before while loop, not inside.

edited Nov 22, 2019 at 8:52

answered Nov 22, 2019 at 8:50

Bart

193 bronze badges

11 Comments

Christopher Over a year ago

While it is not a bad general advice, it does not explain this Compiler error in the least.

Shako Over a year ago

I tried that way as well, but then I get error Use of unassigned local variable CODE

Lukasz Nowakowski Over a year ago

@Christopher - it explains "I've also tried to move return CODE part outside of the while function braces". If only return was moved, than that's the error.

Bart Over a year ago

Also, if you want to return at first loop why use while at all?

Misiakw Over a year ago

compiler tells you exacly what is problem - it's a matter of range of variable. variables defined inside loops, usings, if's etc... can be seen only INSIDE them, not outside. you need to define them outside. then, when defining it outside you simply need to initialize it someway = maybe var CODE = string.Empty;

|

Misiakw · Accepted Answer · 2019-11-22 09:02:35Z

-1

as i mentioned in comment - you should read more about ranges of variables. the one defined inside lambda, whiles, usings, ifs etc... are accesible only there, not outside. this is why if you want to have them outside - vou need to define them outside. also you need to somehow initialize it. try following code:

using (MySqlDataReader rdr = cmd.ExecuteReader())
{
   string CODE = string.Empty;
   while (rdr.Read())
   {
      string result= rdr.GetString(0);
      CODE = Regex.Match(result, @"\d+").Value;
   }
   return CODE ;
}

answered Nov 22, 2019 at 9:02

Misiakw

9228 silver badges28 bronze badges

Collectives™ on Stack Overflow

Unable to return string from while function

3 Answers 3

Comments

11 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

11 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related