建立EF訪問數據庫架構時，出現One or more validation errors were detected during model generation

原因是因為我在寫實體類的時候沒有為實體類中的屬性聲明一個主鍵，即用[key]特性標注在屬性上，這樣DbContext才能為我們在數據庫上找到對應的主鍵

using System.ComponentModel.DataAnnotations.Schema;
using System.ComponentModel.DataAnnotations;
using System;
namespace Feng.Entity
{
    [Serializable]
    [Table("dict_sample")]
    public class Dict_sample
    {
        [Key]//必須要添加的特性，要和數據庫主鍵對應
        [Column("sam_id")]
        [StringLength(12)]
        public string Sam_id
        { get; set; }

        [Column("sam_name")]
        [StringLength(50)]
        public string Sam_name
        { get; set; }

        [StringLength(18)]
        [Column("sam_code")]
        public string Sam_code
        { get; set; }

        [StringLength(12)]
        [Column("sam_incode")]
        public string Sam_incode
        { get; set; }

        [StringLength(12)]
        [Column("sam_type")]
        public string Sam_type
        { get; set; }

        [StringLength(18)]
        [Column("sam_py")]
        public string Sam_py
        { get; set; }

        [StringLength(18)]
        [Column("sam_wb")]
        public string Sam_wb
        { get; set; }

        [Column("sam_seq")]
        public int Sam_seq
        { get; set;
        }

        [StringLength(1)]
        [Column("sam_del")]
        public string Sam_del
        { get; set; }

        [StringLength(18)]
        [Column("sam_custom_type")]
        public string Sam_custom_type
        { get; set; }

        [StringLength(100)]
        [Column("sam_trans_code")]
        public string Sam_trans_code
        { get; set; }

    }
}