How to save select statement values in to local variable in C#

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hello,
i am designed this code in C# asp.net..
My requirement is to select 02 fields from a table and store it to local/session variable .
I have tried many things but nothing worked.

Can anyone help me on this please.

Exp:
select * from CLASS5 where ROLL = 5;

NOW WHAT I WANT IS read the * values like nam e, roll no, address to local variable s

Thank you.

What I have tried:

var alldata = "select REG_fnm,REG_class from Z_REG_OTS where REG_unm = '" + TextBox_signin_unm.Text + "' and REG_pwd= '" + TextBox_signin_pwd.Text + "' ";
SqlCommand cmd1 = new SqlCommand(check, con);
var msg = new List<string>();
using (var reader = cmd1.ExecuteReader())
{
if (reader.HasRows)
{
// if rows present, read
while (reader.Read())
{
var REG_fnm1 = Convert.ToString(reader["REG_fnm"]);
var REG_class1 = Convert.ToString(reader["REG_class"]);
}

}
}

Posted 20-Jul-20 6:56am

sunilrout

Updated 20-Jul-20 8:43am

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Otekpo Emmanuel 20-Jul-20 15:47pm

What is not working? What errors are you having?

1 solution

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OriginalGriff · Answer 1 · 2020-07-20T08:43:00

Not 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?

And another thing ...
Never store passwords in clear text - it is a major security risk. There is some information on how to do it here: Password Storage: How to do it.[^]

And remember: if you have any European Union users then GDPR applies and that means you need to handle passwords as sensitive data and store them in a safe and secure manner. Text is neither of those and the fines can be .... um ... outstanding. In December 2018 a German company received a relatively low fine of €20,000 for just that.