entity framework(EF) 中的Lambda表达式简单应用

entity framework(EF) 中的Lambda表达式简单应用

应用DEMO

List<h_job> list= GetListWhereBy<h_job>(m => m.h_job_id > 2, m => m.h_job_id);

EFModel.dataEntities db;
public publicDAL()
{
this.db = DALBase.GetEntities(); ;
}
public publicDAL(EFModel.dataEntities context)
{
this.db = context;
}
#region 获取列表
/// <summary>
/// 获取列表
/// </summary>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
public List<T> GetList<T>() where T : class
{
try
{
return db.Set<T>().ToList();
}
catch (Exception ex)
{
WriteLog.WriteErrorLog(ex.ToString());
return null;
}
}

/// <summary>
/// 传入条件获取列表
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="whereLambda"></param>
/// <returns></returns>
public List<T> GetList<T>(Expression<Func<T, bool>> whereLambda) where T : class
{
try
{
return db.Set<T>().Where(whereLambda).ToList();
}
catch (Exception ex)
{
WriteLog.WriteErrorLog(ex.ToString());
return null;
}
}

#endregion

#region 根据条件排序获取列表
public List<T> GetListOrderByDesc<T>(Expression<Func<T, bool>> whereLambda, Expression<Func<T, Int32>> orderLambda) where T : class
{
try
{
return db.Set<T>().Where(whereLambda).OrderByDescending(orderLambda).ToList();
}
catch (Exception ex)
{
WriteLog.WriteErrorLog(ex.ToString());
return null;
}
}
public List<T> GetListOrderByDesc<T>(Expression<Func<T, bool>> whereLambda, Expression<Func<T, Int32>> orderLambda, Expression<Func<T, Int32>> orderLambda2) where T : class
{
try
{
return db.Set<T>().Where(whereLambda).OrderByDescending(orderLambda).OrderByDescending(orderLambda2).ToList();
}
catch (Exception ex)
{
WriteLog.WriteErrorLog(ex.ToString());
return null;
}
}
#endregion

#region 增、改、删
/// <summary>
/// 添加
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="model"></param>
/// <returns></returns>
public RetResult Add<T>(T model) where T : class
{
string msg = "操作失败";
string errorMemo = string.Empty;
CmdResultError error = CmdResultError.EXCEPTION;
try
{
db.Set<T>().Add(model);
db.SaveChanges();
error = CmdResultError.NONE;
msg = "操作成功";
}
catch (Exception ex)
{
WriteLog.WriteErrorLog(ex.ToString());
errorMemo = ex.Message;
}
Ret.SetArgument(error, errorMemo, msg);
return Ret;
}
/// <summary>
/// 修改
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="model"></param>
/// <returns></returns>
public RetResult Edit<T>(T model) where T : class
{
string msg = "操作失败";
string errorMemo = string.Empty;
CmdResultError error = CmdResultError.EXCEPTION;
try
{
if (db.Entry<T>(model).State == EntityState.Modified)
{
db.SaveChanges();
}
else if (db.Entry<T>(model).State == EntityState.Detached)
{
try
{
db.Set<T>().Attach(model);
db.Entry<T>(model).State = EntityState.Modified;
}
catch (InvalidOperationException)
{
//T old = Find(model.);
//db.Entry(old).CurrentValues.SetValues(model);
}
db.SaveChanges();
}
error = CmdResultError.NONE;
msg = "操作成功";
}
catch (Exception ex)
{
WriteLog.WriteErrorLog(ex.ToString());
errorMemo = ex.Message;
}
Ret.SetArgument(error, errorMemo, msg);
return Ret;
}
/// <summary>
/// 删除
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="model"></param>
/// <returns></returns>
public RetResult Del<T>(T model) where T : class
{
string msg = "操作失败";
string errorMemo = string.Empty;
CmdResultError error = CmdResultError.EXCEPTION;
try
{
db.Set<T>().Remove(model);
db.SaveChanges();
error = CmdResultError.NONE;
msg = "操作成功";
}
catch (Exception ex)
{
WriteLog.WriteErrorLog(ex.ToString());
errorMemo = ex.Message;
}
Ret.SetArgument(error, errorMemo, msg);
return Ret;
}
/// <summary>
/// 批量删除
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="list"></param>
/// <returns></returns>
public RetResult Del<T>(List<T> list) where T : class
{
string msg = "操作失败";
string errorMemo = string.Empty;
CmdResultError error = CmdResultError.EXCEPTION;
try
{
db.Set<T>().RemoveRange(list);
db.SaveChanges();
error = CmdResultError.NONE;
msg = "操作成功";
}
catch (Exception ex)
{
WriteLog.WriteErrorLog(ex.ToString());
errorMemo = ex.Message;
}
Ret.SetArgument(error, errorMemo, msg);
return Ret;
}
#endregion

参考地址：
http://blog.csdn.net/leftfist/article/details/25005307