使用泛型查询数据小例

在这个例子当中，泛型的出色之处在于，不必为每个类型编写相同的代码讲阅读器的数据转换为泛型List。

1.GenericMethods类

public class GenericMethods
{
    public static List<T> GetListFromCommand<T>(SqlCommand command)
        where T : ICreatable, new()
    {
        List<T> list = new List<T>();
        using (command.Connection)
        {
            command.Connection.Open();
            SqlDataReader dr = command.ExecuteReader();
            while (dr.Read())
            {
                T t = new T();
                t.Create(dr);
                list.Add(t);
            }
        }
        return list;
    }
}

2.Movie实体类

public class Movie : ICreatable
{

    public int ID { get; set; }

    public string Name { get; set; }

    public void Create(SqlDataReader dr)
    {
        ID = int.Parse(dr["ID"].ToString());
        Name = dr["Name"].ToString();
    }
}

3.ICreatable接口

public interface ICreatable
{
    void Create(SqlDataReader dr);
}

4.页面方法调用

 string constring = WebConfigurationManager.ConnectionStrings["sqlconn"].ConnectionString;
        SqlConnection conn = new SqlConnection(constring);
        SqlCommand command = new SqlCommand("SELECT * FROM Movies", conn);
        List<Movie> list = GenericMethods.GetListFromCommand<Movie>(command);