解决使用DbContext保存Decimal数据时总是保留小数位2位问题

通过System.Data.Entity.DbContext保留Decimal类型数据时，默认只保留小数位2位。要解决该问题，可以通过在OnModelCreating事件中添加相应代码即可，具体参考如下代码中将shop.Longitude设置为小数位20位：

public class UserDbContext : System.Data.Entity.DbContext
{
    public UserDbContext()
        : base("MyContext")
    {
        this.Configuration.ProxyCreationEnabled = false;
        this.Configuration.LazyLoadingEnabled = false;
    }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Shop>().Property(shop => shop.Longitude).HasPrecision(30, 20);
        modelBuilder.Entity<Shop>().Property(shop => shop.Latitude).HasPrecision(30, 20);
        modelBuilder.Entity<User>().Property(user => user.ArtificerLatitude).HasPrecision(30, 20);
        modelBuilder.Entity<User>().Property(user => user.ArtificerLongitude).HasPrecision(30, 20);
    } 

    public DbSet<User> Users { get; set; }
    public DbSet<Shop> Shops { get; set; }

}