Update a value in a mysql database in ASP.NET

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I am able to store data in the database, but I am unable to update values in it. I have a table with 5 values, which are name, user, password, title, and project, and I need to be able to update the password, just by entering the user.
I tried this code:

String connString = System.Configuration.ConfigurationManager.ConnectionStrings["web"].ToString();
        conn = new MySql.Data.MySqlClient.MySqlConnection(connString);
        conn.Open();
        //queryStr = "";
        cmd = conn.CreateCommand();
        cmd.CommandType = System.Data.CommandType.Text;
        queryStr = "UPDATE meal.claves set usuario='" + user.Text+"where clave ='"+pass+"'";
        cmd = new MySql.Data.MySqlClient.MySqlCommand("update meal.claves Set usuario=@user,clave=@pass");
        //cmd = new MySql.Data.MySqlClient.MySqlCommand(queryStr, conn);
        //cmd.ExecuteReader();
            cmd.ExecuteNonQuery();
        
        conn.Close();

Got error saying connection must be open and valid.

What I have tried:

I tried the code in this video:
https://www.youtube.com/watch?v=sggbk2ES8DM

Posted 24-Nov-17 6:21am

Member 10850253

Updated 24-Nov-17 9:30am

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CHill60 · Answer 1 · 2017-11-24T09:16:00

Solution 1

Clue

C#

cmd = new ...

. Your new cmd does not have a connection.
Also, do not concatenate strings to form sql command strings...use command parameters

Posted 24-Nov-17 9:16am

CHill60

Patrice T · Answer 2 · 2017-11-24T09:30:00

C#

queryStr = "UPDATE meal.claves set usuario='" + user.Text+"where clave ='"+pass+"'";

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[^]