mvc+dwz第三天

再DAL类库中封装BaseDAL

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using System.Linq.Expressions;
using System.Reflection;
using Xiaowu.Model;
namespace Xiaowu.DAL
{
public class BaseDAL<T> where T : class
{
StudentDBContext dbcontext = new StudentDBContext();
/// <summary>
/// IQueryable延迟加载集合，调用时才回去加载到内存
/// List查找会立即加载到内存
/// </summary>
/// <returns></returns>
public IQueryable<T> GetEntitys(Expression<Func<T, bool>> Lambdawhere)
{
return dbcontext.Set<T>().Where(Lambdawhere);
}

/// <summary>
/// 新增
/// </summary>
/// <param name="entity"></param>
/// <returns></returns>
public int Add(T entity)
{
dbcontext.Set<T>().Add(entity);
return dbcontext.SaveChanges();
}

/// <summary>
/// 删除
/// </summary>
/// <param name="id"></param>
/// <returns></returns>
public int Delete(int id)
{
//通过ID查询这个实体
T entity = dbcontext.Set<T>().Find(id);
dbcontext.Set<T>().Remove(entity);
return dbcontext.SaveChanges();
}

/// <summary>
/// 修改
/// </summary>
/// <param name="id"></param>
/// <returns></returns>
public int Update(T entity)
{
//设置当前实体粘状态
dbcontext.Entry(entity).State = System.Data.Entity.EntityState.Modified;
return dbcontext.SaveChanges();
}

/// <summary>
/// 修改2/add/2020/11/16
/// </summary>
/// <param name="id"></param>
/// <returns></returns>
public int Update2(T entity)
{
dbcontext.Set<T>().Attach(entity);
PropertyInfo[] props = entity.GetType().GetProperties();
foreach (PropertyInfo prop in props)
{
if (prop.GetValue(entity, null) != null)
{
if (prop.GetValue(entity, null).ToString() == " ")
dbcontext.Entry(entity).Property(prop.Name).CurrentValue = null;
dbcontext.Entry(entity).Property(prop.Name).IsModified = true;
}
}
return dbcontext.SaveChanges();
}

#region 分页查询/add/2020/11/16
/// <summary>
/// Entities的分页数据查询
/// </summary>
/// <typeparam name="S">Orderby根据排序的元素数据类型</typeparam>
/// <param name="pageIndex">要查询到页码</param>
/// <param name="pageSize">每页的条数</param>
/// <param name="total">总条数</param>
/// <param name="whereLambda">过滤数据的Lambda表达式</param>
/// <param name="orderByLambda">指定排序规则的Lambda表达式</param>
/// <param name="IsAsc">是否是升序排序？</param>
/// <returns></returns>
public IQueryable<T> GetPageEntities<S>(int pageIndex, int pageSize, out int total, Expression<Func<T, bool>> whereLambda, Expression<Func<T, S>> orderByLambda, bool IsAsc)
{
total = dbcontext.Set<T>().Where(whereLambda).Count();
if (IsAsc)
{
return dbcontext.Set<T>().Where(whereLambda).OrderBy<T, S>(orderByLambda).Skip((pageIndex - 1) * pageSize).Take(pageSize).AsQueryable();

}
else
{
return dbcontext.Set<T>().Where(whereLambda).OrderByDescending<T, S>(orderByLambda).Skip((pageIndex - 1) * pageSize).Take(pageSize).AsQueryable();

}
}

#endregion
}
}