using System.Windows.Media;
using System.Windows.Media.Imaging;

 using (SqlConnection conn=new SqlConnection("Data Source=.;Initial Catalog=imageprocess;Integrated Security=True"))
            {
                conn.Open();
                using(SqlCommand cmd=conn.CreateCommand())
                {
                    cmd.CommandText = "select count(*) from [user]";
                    int i = (int)cmd.ExecuteScalar();
                    MessageBox.Show(i.ToString());
                }//这个括号结束的时候自动释放SqlCommand
            }//这个括号结束的时候自动释放SqlConnection

using System;
using aClass = NameSpace1.MyClass;
using bClass = NameSpace2.MyClass;
 
namespace NameSpace1 
{
    public class MyClass 
    {
        public override string ToString() 
        {
            return "You are in NameSpace1.MyClass";
        }
    }
}
 
namespace NameSpace2 
{
    class MyClass 
    {
        public override string ToString() 
        {
            return "You are in NameSpace2.MyClass";
        }
    }
}
 
namespace testUsing
{
    using NameSpace1;
    using NameSpace2;
    /// <summary>
    /// Class1 的摘要说明。
    /// </summary>
    class Class1
    {
        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main(string[] args)
        {
            //
            // TODO: 在此处添加代码以启动应用程序
            //
 
            aClass my1 = new aClass();
            Console.WriteLine(my1);
            bClass my2 = new bClass();
            Console.WriteLine(my2);
            Console.WriteLine("Press any key");
            Console.Read();
        }
    }
}