Problem with update data into SQL database in ASP

Quote:

i try change the database query

That would be a very good idea. 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:

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:

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

Which SQL sees as three separate commands:

SELECT * FROM MyTable WHERE StreetAddress = 'x';

A perfectly valid SELECT

DROP TABLE MyTable;

A perfectly valid "delete the table" command

--'

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 when you've fixed that through your whole app, you can start looking at teh problem you have noticed: SQL Syntax.

UPDATE MyTable SET MyColumn = myValue WHERE MyOtherColumn = MyOtherValue

Quote:

Thank you, bu could you help me how use Parameterized queries? I am beginner programist and i don't have idea

using (SqlConnection con = new SqlConnection(strConnect))
    {
    con.Open();
    using (SqlCommand com = new SqlCommand("UPDATE myTable SET myColumn1=@C1, myColumn2=@C2 WHERE Id=@ID", con))
        {
        com.Parameters.AddWithValue("@ID", id);
        com.Parameters.AddWithValue("@C1", myValueForColumn1);
        com.Parameters.AddWithValue("@C2", myValueForColumn2);
        com.ExecuteNonQuery();
        }
    }

int z;
if (!int.TryParse(TextBox1.Text, out z))
{
    // TODO: Display an error to the user
    return;
}

using (var connection = new SqlConnection("..."))
using (var command = new SqlCommand("UPDATE zapasy SET ilosc = ilosc + @z OUTPUT inserted.ilosc WHERE login = @login And odmiana = @odmiana", connection))
{
    command.Parameters.AddWithValue("@z", z);
    command.Parameters.AddWithValue("@login", Context.User.Identity.Name);
    command.Parameters.AddWithValue("@odmiana", odmiany.SelectedValue);
    
    connection.Open();
    object result = command.ExecuteScalar();
    stani.Text = Convert.ToString(result);
}