Simple DB layer example, if not possible to use ORM or domain-driven design.

simpleDbLayer.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace DbLayerSample
{
    class Program
    {
        static void Main(string[] args)
        {
            Database dB = new Database();

            dB.Query<InsertStudent>().Where(student => student.Name = "Stan").Execute();

            Console.ReadLine();
        }
    }


    public class Database
    {
        //ignoring how to get connection strings.

        public Database<T> Query<T>() where T : IQuery, new() // 
        {
            return new Database<T>("some connection string");
        }
    }
    public class Database<T> where T : IQuery, new()
    {
        public string ConnectionString { get; private set; }
        private readonly T query;

        public Database(string connectionString)
        {
            this.ConnectionString = connectionString;
            this.query = new T(); // <-- new() constraint allows me to it
        }

        public Database<T> Where(Action<T> filler)
        {
            filler(query);

            return this;
        }

        public bool Execute()
        {
            Console.WriteLine("Execute: {0}", query.SqlCommandText);
            return true;
        }
    }
    public class InsertStudent : IQuery
    {
        public string Name { get; set; }

        public string SqlCommandText
        {
            get
            {
                return string.Format("insert name = {0} into students", this.Name);
            }
        }
    }
    public interface IQuery
    {
        string SqlCommandText { get; }
    }
}