linqHelper(随便写写,参照别人的)

最新推荐文章于 2022-11-17 03:15:00 发布

转载最新推荐文章于 2022-11-17 03:15:00 发布 · 1.6k 阅读

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#LinqHelper

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本文介绍了一个名为linqHelper的抽象类，用于通过LINQ查询和操作数据库。包括查询全部数据、检查数据存在性、过滤数据、插入数据、删除数据等功能。

using System;  
using System.Data;  
using System.Configuration;  
using System.Linq;  
using System.Web;  
using System.Xml.Linq;  
using System.Collections.Generic;  
using System.Linq.Expressions;  
using System.Data.Linq;  
using Database;  
/// <summary>   
///linqHelper 的摘要说明   
/// </summary>   
namespace Business  
{  
    public abstract class linqHelper<TDatabase>  
where TDatabase : DataContext, new()  
    {  
        /// <summary>   
        /// 查询全部数据   
        /// </summary>   
        /// <typeparam name="T"></typeparam>   
        /// <returns></returns>   
        public static List<T> ReturnAllRows<T>(string conString) where T : class  
        {  
            TDatabase database = new TDatabase();  
            database.Connection.ConnectionString = conString;  
            return database.GetTable<T>().ToList<T>();  
        }  
        /// <summary>   
        /// 查看是否存在数据   
        /// </summary>   
        /// <typeparam name="T"></typeparam>   
        /// <param name="predicate"></param>   
        /// <returns></returns>   
        public static bool EntityExists<T>(string conString,Expression<Func<T, bool>> predicate)  
        where T : class  
        {  
            TDatabase database = new TDatabase();  
            database.Connection.ConnectionString = conString;  
            return database.GetTable<T>().Where<T>(predicate).Count() > 0;  
        }  
        /// <summary>   
        /// 有条件的查询数据List<typeparamref name="数据源:DataContext"/>  Filter<typeparamref name="表的类名:orders"/>    
        /// 最后面的可以输入LINQ查询语句（p=>p.order_id="00001")或者(form o in orders where o.order_id>100 sleect o);   
        /// </summary>   
        /// <typeparam name="T"></typeparam>   
        /// <param name="predicate"></param>   
        /// <returns></returns>   
        public static List<T> Filter<T>(string conString,Expression<Func<T, bool>> predicate)  
        where T : class  
        {  
            TDatabase database = new TDatabase();  
              
            database.Connection.ConnectionString = conString;  
            return database.GetTable<T>().Where(predicate).ToList<T>();  
        }  
        /// <summary>   
        /// 插入数据,好象只能一条,测试完弄个数据插入多条   
        /// </summary>   
        /// <typeparam name="T"></typeparam>   
        /// <param name="entity"></param>   
        public static void Insert<T>(string conString,T entity) where T : class  
        {  
            using (TDatabase database = new TDatabase())  
            {  
                database.Connection.ConnectionString = conString;  
                database.GetTable<T>().InsertOnSubmit(entity);  
                database.SubmitChanges();  
            }  
        }  
        /// <summary>   
        /// 删除指定数据,支持多条删除  Expression<Func<T, bool>> predicate就是查询语句，只能用：p=>p.user_id=="123"的语句！   
        /// </summary>   
        /// <typeparam name="T"></typeparam>   
        /// <param name="predicate"></param>   
        ///返回值：0 成功    -1 失败   
        public static int Delete<T>(string conString,Expression<Func<T, bool>> predicate)  
        where T : class  
        {  
            if (EntityExists<T>(conString, predicate))  
            {  
                using (TDatabase database = new TDatabase())  
                {  
                    database.Connection.ConnectionString = conString;  
                    T t = (T)database.GetTable<T>().Where<T>(predicate).Single();  
                    database.GetTable<T>().DeleteOnSubmit(t);  
                    database.SubmitChanges();  
                }  
                return 0;  
            }  
            return -1;  
        }  
        /// <summary>   
        /// 返回分页面数据   
        /// </summary>   
        /// <typeparam name="T"></typeparam>   
        /// <param name="pageSize">一次取多少条数据</param>   
        /// <param name="currerCount">当前提交的页数字</param>   
        /// <returns></returns>   
        public static List<T> getpPgeRow<T>(string conString,int pageSize, int currerCount) where T : class  
        {  
            TDatabase database = new TDatabase();  
            database.Connection.ConnectionString = conString;  
            return database.GetTable<T>().Skip<T>((currerCount - 1) * pageSize).Take<T>(pageSize).ToList<T>();  
        }  
        /// <summary>   
        /// 返回多少条数据   
        /// </summary>   
        /// <typeparam name="T"></typeparam>   
        /// <param name="predicate"></param>   
        /// <returns></returns>   
        public static int getPageCount<T>(string conString,Expression<Func<T, bool>> predicate) where T : class  
        {  
            TDatabase database = new TDatabase();  
            database.Connection.ConnectionString = conString;  
            return database.GetTable<T>().Where<T>(predicate).Count();  
        }  
        /// <summary>   
        /// 一次插入多条数据    
        /// </summary>   
        /// <typeparam name="T"></typeparam>   
        /// <param name="entity"></param>   
        public static void insetRows<T>(string conString,List<T> entity) where T : class  
        {  
            using (TDatabase database = new TDatabase())  
            {  
                database.Connection.ConnectionString = conString;  
                foreach(T t in entity.ToList())  
                {  
                    database.GetTable<T>().InsertOnSubmit(t);  
                    database.SubmitChanges();  
                }  
                 
            }  
        }  
    }  
}

)