Simple code for Provider Model pattern along with Singleton pattern using C#

Here is the sample code for Provider Model pattern along with Singleton pattern using C#.

public abstract class TestProviderBase : System.Configuration.Provider.ProviderBase
    {
        public abstract List<Test> GetAllTests();
    }

public class TestProvider : TestProviderBase
    {
        public override List<Test> GetAllTests()
        {
            string connString = ConfigurationManager.ConnectionStrings["AppConnectionString1"].ConnectionString;
            using (SqlConnection conn = new SqlConnection(connString))
            {
                conn.Open();
                using (SqlCommand command = new SqlCommand("select dbo.Test.ColA,dbo.Test.ColB from dbo.Test", conn))
                {
                    return Common.ConvertReaderToTest(command.ExecuteReader());
                }
            }
           
        }
    }

public sealed class TestServices
    {
        static TestProvider testInstance = null;
        static readonly object padlock = new object();

        TestServices()
        {

        }
        public static TestProvider provider
        {
            get
            {
                lock (padlock)
                {
                    if (testInstance == null)
                    {
                        testInstance = new TestProvider();
                    }
                    return testInstance;
                }

            }
        }

    }

Code to execute:

GridView1.DataSource = TestServices.provider.GetAllTests();
 GridView1.DataBind();