linqHelper(随便写写,参照别人的)

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();

}

}

}

}

}