What is the good way to write this in C#?

Question

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C#

string query2 = "select * from [next] where id='" + txtCIVILIDD.Text + "'";
            SqlCommand command = new SqlCommand(query2, con);
            SqlDataAdapter adapter = new SqlDataAdapter(command);
            con.Open();
            command = new SqlCommand("INSERT INTO next (id,time,clock,username,Name_Arabic,gender) VALUES('" + txtCIVILIDD.Text + "','" + txttime.Text + "','" + txtclock.Text + "','" + txtusername.Text + "','" + txtName_Arabic.Text + "','" + CBgender.Text + "')", con);
            command.ExecuteNonQuery();
            con.Close();

im new in coding i want to find what is the good way to write this code in my c# program someone tell me that way is wrong but it work good for me so i want to know why ??

What I have tried:

i don't know the good way for it i know that i have sql injection

Posted 23-Jan-19 20:45pm

el_tot93

Updated 24-Jan-19 1:37am

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4 solutions

Solution 3

C#

command = new SqlCommand("INSERT INTO next (id,time,clock,username,Name_Arabic,gender) VALUES('" + txtCIVILIDD.Text + "','" + txttime.Text + "','" + txtclock.Text + "','" + txtusername.Text + "','" + txtName_Arabic.Text + "','" + CBgender.Text + "')", con);

Your code is subject to SQL Injection.
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[^]
How can I explain SQL injection without technical jargon? - Information Security Stack Exchange[^]

Posted 24-Jan-19 0:23am

Patrice T

Comments

MadMyche 24-Jan-19 7:14am

5'd. And the poster has received this same information a few times now

Patrice T 24-Jan-19 7:16am

Thank you.

Solution 2

The best way would be to use String.Format property or use a stored procedure to prevent SQL injection.

Posted 23-Jan-19 22:34pm

Ammar_Ahmad

Comments

Richard MacCutchan 24-Jan-19 4:54am

No, the proper way is to use parameterised queries, as explained by Pete above.

MadMyche 24-Jan-19 7:11am

+1

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Pete O'Hanlon · Accepted Answer · 2019-01-23T20:55:00

At a quick glance, there are a couple of issues in your code. The first thing is that your code is wide open to something known as a Sql Injection Attack. This[^] article explains what they are and how you can prevent them.

The second thing is that you have code in there that you cannot guarantee will call Dispose when you are finished with resources. This means that resources may not be released, which can lead to things like memory leaks or resource starvation (which means that a resource you rely on, such as a database connection, may be unavailable to you because you have used them all up). The common way to solve this problem is to use a using statement to wrap up objects that implement IDisposable. Something like this:

C#

using (SqlConnection con = new SqlConnection(myConnectionString))
{
  // Do my work
} // When the application reaches this point, it will automatically call con.Dispose()

Richard Deeming · Accepted Answer · 2019-01-24T01:37:00

As others have pointed out, your code is vulnerable to SQL Injection. But you already knew that! :)

I believe you just wanted an example of how to fix the vulnerability:

C#

using (SqlConnection con = new SqlConnection(myConnectionString))
{
    con.Open();
    
    // INSERT command:
    using (SqlCommand command = new SqlCommand("INSERT INTO [next] (id, time, clock, username, Name_Arabic, gender) VALUES (@id, @time, @clock, @username, @Name_Arabic, @gender)", con))
    {
        // TODO: Convert the text to an appropriate type, if necessary:
        command.Parameters.AddWithValue("@id", txtCIVILIDD.Text);
        command.Parameters.AddWithValue("@time", txttime.Text);
        command.Parameters.AddWithValue("@clock", txtclock.Text);
        command.Parameters.AddWithValue("@username", txtusername.Text);
        command.Parameters.AddWithValue("@Name_Arabic", txtName_Arabic.Text);
        command.Parameters.AddWithValue("@gender", CBgender.Text);
        
        command.ExecuteNonQuery();
    }
    
    // SELECT command:
    using (SqlCommand command = new SqlCommand("SELECT * FROM [next] WHERE id = @id", con))
    {
        // TODO: As above, convert the text to an appropriate type if necessary:
        command.Parameters.AddWithValue("@id", txtCIVILIDD.Text);
        
        SqlDataAdapter adapter = new SqlDataAdapter(command);
        DataSet data = new DataSet();
        adapter.Fill(data);
        
        // TODO: Do something with the loaded data here...
    }
}

NB: As pointed out in the comments, you may encounter problems if the text in your controls can't be converted to the appropriate types for the columns. If necessary, you will need to validate the text and/or convert it to an appropriate type before adding the parameters.

Some light reading for you:
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[^]