SQL/C# - Best method for executing a query

Question

I need to execute a sql query from within a c# class. I have thought of 2 options

1. Starting a process of sqlcmd.
2. Using a SqlCommand object.

Answer 1

Use a SqlCommand. This code will only keep the connection alive for a very short period of time (as long as your query is performant):

DataTable results = new DataTable();

using(SqlConnection conn = new SqlConnection(connString))
    using(SqlCommand command = new SqlCommand(query, conn))
        using (SqlDataAdapter dataAdapter = new SqlDataAdapter(command))
           dataAdapter.Fill(results);