Linq通用分页数据查询方法

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Linq通用分页数据查询方法

cdboy · 2013-01-19 · via 博客园 - cdboy

在使用EF的过程有很多需要分页查询数据的地方，但是经常重复在输入分页的相关代码，这样即不便于维护，也增加了不少工作量。

对于通用查询有几个要点，一是要动态定义查询条件，还可以动态选择所需要的列。

1、数据查询方法

Code Snippet

publicstaticList<TResult> Query<TEntity, TOrderBy, TResult>(thisIQueryable<TEntity> query,
Expression<Func<TEntity, bool>> where,
Expression<Func<TEntity, TOrderBy>> orderby,
Expression<Func<TEntity, int, TResult>> selector,
bool isAsc)

Code Snippet

publicstaticList<object> Query<TEntity, TOrderBy>(thisIQueryable<TEntity> query,
Expression<Func<TEntity, bool>> where,
Expression<Func<TEntity, TOrderBy>> orderby,
Func<IQueryable<TEntity>, List<object>> selector,
bool isAsc)

Code Snippet

publicstaticPageInfo<object> Query<TEntity, TOrderBy>(thisIQueryable<TEntity> query, int index, int pageSize,
Expression<Func<TEntity, bool>> where,
Expression<Func<TEntity, TOrderBy>> orderby,
Func<IQueryable<TEntity>, List<object>> selector,
bool isAsc)

3、分页查询方法

Code Snippet

publicstaticPageInfo<object> Query<TEntity, TOrderBy>(thisIQueryable<TEntity> query, int index, int pageSize,
List<Expression<Func<TEntity, bool>>> wheres,
Expression<Func<TEntity, TOrderBy>> orderby,
Func<IQueryable<TEntity>, List<object>> selector, bool isAsc)

Code Snippet

publicstaticPageInfo<TResult> Query<TEntity, TOrderBy, TResult>(thisIQueryable<TEntity> query, int index, int pageSize,
List<Expression<Func<TEntity, bool>>> wheres,
Expression<Func<TEntity, TOrderBy>> orderby,
Func<IQueryable<TEntity>, List<TResult>> selector, bool isAsc)

Code Snippet

publicstaticPageInfo<TResult> Query<TEntity, TOrderBy, TResult>(thisIQueryable<TEntity> query, int index, int pageSize,
Expression<Func<TEntity, bool>> where,
Expression<Func<TEntity, TOrderBy>> orderby,
Func<IQueryable<TEntity>, List<TResult>> selector,
bool isAsc)

工具类方法：

Code Snippet

publicclassPageInfo
{
publicstaticvoid CheckPageIndexAndSize(refint index, refint size)
{
if (index < 1)
{
index = 1;
}
if (size < 1)
{
size = 20;
}
}
publicstaticvoid CheckPageIndexAndSize(refint index, int size, int count)
{
if (count >= index * size)
{
return;
}
index = count / size;
if (count % size > 0)
{
index++;
}
if (index == 0)
{
index = 1;
}
}
}
publicclassPageInfo<T> : PageInfo
{
internal PageInfo()
{
DataList = newList<T>();
}
public PageInfo(int index, int pageSize, int count, List<T> dataList)
{
Index = index;
PageSie = pageSize;
Count = count;
DataList = dataList;
}
publicint Index { get; privateset; }
publicint PageSie { get; privateset; }
publicint Count { get; privateset; }
publicList<T> DataList { get; privateset; }
publicPageInfo<T> Empty
{
get { returnnewPageInfo<T>(); }
}
}

实现代码：

Code Snippet

publicstaticclassLinqExtent
{
publicstaticList<TResult> Query<TEntity, TOrderBy, TResult>(thisIQueryable<TEntity> query,
Expression<Func<TEntity, bool>> where,
Expression<Func<TEntity, TOrderBy>> orderby,
Expression<Func<TEntity, int, TResult>> selector,
bool isAsc)
{
if (selector == null)
{
thrownewArgumentNullException("selector");
}
var queryable = query;
if (where != null)
{
queryable = queryable.Where(where);
}
if (orderby != null)
{
queryable = isAsc ? queryable.OrderBy(orderby) : queryable.OrderByDescending(orderby);
}
return queryable.Select(selector).ToList();
}
publicstaticList<object> Query<TEntity, TOrderBy>(thisIQueryable<TEntity> query,
Expression<Func<TEntity, bool>> where,
Expression<Func<TEntity, TOrderBy>> orderby,
Func<IQueryable<TEntity>, List<object>> selector,
bool isAsc)
{
if (selector == null)
{
thrownewArgumentNullException("selector");
}
var queryable = query;
if (where != null)
{
queryable = queryable.Where(where);
}
if (orderby != null)
{
queryable = isAsc ? queryable.OrderBy(orderby) : queryable.OrderByDescending(orderby);
}
return selector(queryable);
}
publicstaticPageInfo<object> Query<TEntity, TOrderBy>(thisIQueryable<TEntity> query, int index, int pageSize,
Expression<Func<TEntity, bool>> where,
Expression<Func<TEntity, TOrderBy>> orderby,
Func<IQueryable<TEntity>, List<object>> selector,
bool isAsc)
{
return Query(query, index, pageSize, newList<Expression<Func<TEntity, bool>>> {where}, orderby, selector,
isAsc);
}
publicstaticPageInfo<object> Query<TEntity, TOrderBy>(thisIQueryable<TEntity> query, int index, int pageSize,
List<Expression<Func<TEntity, bool>>> wheres,
Expression<Func<TEntity, TOrderBy>> orderby,
Func<IQueryable<TEntity>, List<object>> selector, bool isAsc)
{
//if (selector == null)
//{
// throw new ArgumentNullException("selector");
//}
//PageInfo.CheckPageIndexAndSize(ref index,ref pageSize);
//IQueryable<TEntity> queryable = query;
//if (wheres != null)
//{
// wheres.ForEach(p=>queryable = queryable.Where(p));
//}
//int count = query.Count();
//PageInfo.CheckPageIndexAndSize(ref index,pageSize,count);
//if (count > 0)
//{
// if (orderby != null)
// {
// queryable = isAsc ? queryable.OrderBy(orderby) : queryable.OrderByDescending(orderby);
// }
// return new PageInfo<object>(index,pageSize,count,selector(queryable));
//}
//return new PageInfo<object>(index,pageSize,count,new List<object>());
return Query<TEntity, TOrderBy, object>(query, index, pageSize, wheres, orderby, selector, isAsc);
}
publicstaticPageInfo<TResult> Query<TEntity, TOrderBy, TResult>(thisIQueryable<TEntity> query, int index, int pageSize,
List<Expression<Func<TEntity, bool>>> wheres,
Expression<Func<TEntity, TOrderBy>> orderby,
Func<IQueryable<TEntity>, List<TResult>> selector, bool isAsc)
{
if (selector == null)
{
thrownewArgumentNullException("selector");
}
PageInfo.CheckPageIndexAndSize(ref index, ref pageSize);
IQueryable<TEntity> queryable = query;
if (wheres != null)
{
wheres.ForEach(p => queryable = queryable.Where(p));
}
int count = query.Count();
PageInfo.CheckPageIndexAndSize(ref index, pageSize, count);
if (count > 0)
{
if (orderby != null)
{
queryable = isAsc ? queryable.OrderBy(orderby) : queryable.OrderByDescending(orderby);
}
returnnewPageInfo<TResult>(index, pageSize, count, selector(queryable));
}
returnnewPageInfo<TResult>(index, pageSize, count, newList<TResult>());
}
publicstaticPageInfo<TResult> Query<TEntity, TOrderBy, TResult>(thisIQueryable<TEntity> query, int index, int pageSize,
Expression<Func<TEntity, bool>> where,
Expression<Func<TEntity, TOrderBy>> orderby,
Func<IQueryable<TEntity>, List<TResult>> selector,
bool isAsc)
{
return Query(query, index, pageSize, newList<Expression<Func<TEntity, bool>>> { where }, orderby, selector,
isAsc);
}
}

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