c# - When should I open and close a connection to SQL Server

Question

I have a simple static class with a few methods in it. Each of those methods open a SqlConnection, query the database and close the connection. This way, I am sure that I always close the connection to the database, but on the other hand, I don't like to always open and close connection. Below is an example of what my methods look like.

public static void AddSomething(string something)
{
    using (SqlConnection connection = new SqlConnection("..."))
    {
        connection.Open();
        // ...
        connection.Close();
    }
}

Considering that the methods are inside a static class, should I have a static member containing a single SqlConnection? How and when should I drop it? What are the best practices?

Answer 1

No, don't keep a static SqlConnection unless you have to. Threading would be one concern, but more importantly - usually you simply don't need to. With your code as presented, the internal connection pooling means that most of the time you will get the same underlying connection on successive calls anyway (as long as you use the same connection string). Let the pooler do its job; leave the code alone.

This also avoids the issues of what happens when you start having two threads... now each can do work on their own connection; with static (assuming you don't use [ThreadStatic]) you'd have to synchronize, introducing delays. Not to mention re-entrancy (i.e. a single thread trying to use the same connection twice at the same time). Yup; leave the code alone. It is fine now, and almost any change you make would make it not fine.