Connection open and connection close

Question

1.00/5 (1 vote)

See more:

Hello, i am begineer software developer and i want collect information about programming that's why i have a question that why we use connection.open and connection.close in c# on every single query of database i want to know about that please give me the answer with the logical answer so may be i will understannd better

What I have tried:

C#

connection.Open();
            DataSet dsa = new DataSet();
            DataTable dt = new DataTable();
            dsa.Tables.Add(dt);
            OleDbDataAdapter da = new OleDbDataAdapter();
            da = new OleDbDataAdapter("SELECT [User Name] FROM Login where [User Code] = " + comboBox1.Text + " ", connection);
            da.Fill(dt);
            //dataGridView1.DataSource = dt;
            textBox1.Text = dt.Rows[0][0].ToString();
            connection.Close();

Posted 7-Dec-16 12:38pm

Member 9983063

Updated 7-Dec-16 13:17pm

v2

Add a Solution

Comments

PIEBALDconsult 7-Dec-16 18:59pm

A DataAdapter will Open and Close the Connection for you automatically. But please don't use DataAdapters; they suck.

PIEBALDconsult 7-Dec-16 19:17pm

0) Please learn to use parameters -- never use string concatenation to provide values.
1) If you want only one value from the database; please look into ExecuteScalar.

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Dave Kreskowiak · Answer 1 · 2016-12-07T13:17:00

This has nothing to do with C#, but with cost. SQL servers are very expensive beasts and connection licenses were finite and well as other resources on the server. It's your job as a programmer to limit your use of licenses and server resources. So you do that by opening a connection as late as possible, executing your query as quickly and efficiently as possible, and closing the connection as early as possible, freeing up the resources you used for some other query.

This applies in all languages, not just C#.