DAL/BookManagementDAL.cs

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using DAL.Register;
using Model;
using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Utils;

namespace DAL
{
    /// <summary>
    /// 图书管理数据访问类
    /// </summary>
    public class BookManagementDAL
    {
        /// <summary>
        /// 图书分类
        /// </summary>
        /// <returns></returns>
        public DataTable ShowDAL()
        {
            string sql = $"select ID,CategoryID,CategoryName,ParentID from BookCategory";
            return SQLHelper.Query(sql,null);
        }

      
        /// <summary>
        /// 获取父类
        /// </summary>
        /// <returns></returns>
        public DataTable FindParentDAL()
        {
            string sql = "SELECT * FROM BookCategory WHERE ParentID=@Parentid";
            SqlParameter[] par = { new SqlParameter("@Parentid", "0") };
            return SQLHelper.Query(sql, par);
        }

        /// <summary>
        /// 获取子类
        /// </summary>
        /// <returns></returns>
        public DataTable FindsonDAL()
        {
            string sql = "SELECT * FROM BookCategory WHERE ParentID!=@Parentid";

            SqlParameter[] par = { new SqlParameter("@Parentid", "0") };
            return SQLHelper.Query(sql, par);
        }

        /// <summary>
        /// 图书列表及搜索
        /// </summary>
        /// <param name="BookID">图书id</param>
        /// <returns></returns>
        public DataTable getBookbyidDAL(string BookID)
        {
            string sqls = BookID == "" ? "" : "WHERE b.BookID = @BookID";