linq 常用语句
自己练习的
switch (productDataAnalysisQuery.DataType)
{
case :
var data = (from hp in GPEcontext.hbl_product
join hcim in
from hci in GPEcontext.hbl_change_info
where hci.LotNum == && hci.ChangeData <
&& hci.CreatedTime >= beginDate && hci.CreatedTime <= endDate
group hci by new { hci.ProductId } into G
select new
{
ProductId = G.Key.ProductId,
Amount = G.Sum(item => Math.Abs(item.ChangeData.Value))
} on hp.id equals hcim.ProductId
orderby hcim.Amount descending
select new ProductDataAnalysisodel
{
ProductName = hp.ProductName,
ProductCode = hp.ProductCode,
Amount = hcim.Amount
}).Take();
pageModel.Models = data.FindBy(item => true, productDataAnalysisQuery.PageNo, productDataAnalysisQuery.PageSize, out total, item => item.Amount, false);
break;
case :
var data2 = (from hp in GPEcontext.hbl_product
join hcim in
from hci in GPEcontext.hbl_change_info
where hci.LotNum == && hci.ChangeData <
&& hci.CreatedTime >= beginDate && hci.CreatedTime <= endDate
group hci by new { hci.ProductId } into G
select new
{
ProductId = G.Key.ProductId,
Amount = G.Sum(item => Math.Abs(item.ChangeData.Value))
} on hp.id equals hcim.ProductId
orderby hcim.Amount
select new ProductDataAnalysisodel
{
ProductName = hp.ProductName,
ProductCode = hp.ProductCode,
Amount = hcim.Amount
}).Take();
pageModel.Models = data2.FindBy(item => true, productDataAnalysisQuery.PageNo, productDataAnalysisQuery.PageSize, out total, item => item.Amount, false);
break;
case :
var data3 = (from hp in GPEcontext.hbl_product
join hcim in
from hci in GPEcontext.hbl_change_info
where hci.LotNum == && hci.ChangeData <
&& hci.CreatedTime >= beginDate && hci.CreatedTime <= endDate
group hci by new { hci.ProductId } into G
select new
{
ProductId = G.Key.ProductId,
Amount = G.Count()
} on hp.id equals hcim.ProductId
orderby hcim.Amount descending
select new ProductDataAnalysisodel
{
ProductName = hp.ProductName,
ProductCode = hp.ProductCode,
Amount = hcim.Amount
}).Take();
pageModel.Models = data3.FindBy(item => true, productDataAnalysisQuery.PageNo, productDataAnalysisQuery.PageSize, out total, item => item.Amount, false); break;
case :
var data4 = (from hp in GPEcontext.hbl_product
join hcim in
from hci in GPEcontext.hbl_change_info
where hci.LotNum == && hci.ChangeData <
&& hci.CreatedTime >= beginDate && hci.CreatedTime <= endDate
group hci by new { hci.ProductId } into G
select new
{
ProductId = G.Key.ProductId,
Amount = G.Count()
} on hp.id equals hcim.ProductId
orderby hcim.Amount
select new ProductDataAnalysisodel
{
ProductName = hp.ProductName,
ProductCode = hp.ProductCode,
Amount = hcim.Amount
}).Take();
pageModel.Models = data4.FindBy(item => true, productDataAnalysisQuery.PageNo, productDataAnalysisQuery.PageSize, out total, item => item.Amount, false); break;
case :
var data5 = (from hp in GPEcontext.hbl_product
join hs in
from hps2 in GPEcontext.hbl_product_stock
join p in
from hps in GPEcontext.hbl_product_stock
group hps by new { hps.ProductID } into G
select new
{
ProductId = G.Key.ProductID,
CreatedTime = G.Max(p => p.CreatedTime)
}
on new { A = hps2.ProductID, B = hps2.CreatedTime } equals new { A = p.ProductId, B = p.CreatedTime }
select new
{
ProductId = hps2.ProductID,
Amount = hps2.Stock
}
on hp.id equals hs.ProductId
orderby hs.Amount descending
select new ProductDataAnalysisodel
{
ProductName = hp.ProductName,
ProductCode = hp.ProductCode,
Amount = hs.Amount.Value
}).Take();
pageModel.Models = data5.FindBy(item => true, productDataAnalysisQuery.PageNo, productDataAnalysisQuery.PageSize, out total, item => item.Amount, false); break;
case :
var data6 = (from hp in GPEcontext.hbl_product
join hs in
from hps2 in GPEcontext.hbl_product_stock
join p in
from hps in GPEcontext.hbl_product_stock
group hps by new { hps.ProductID } into G
select new
{
ProductId = G.Key.ProductID,
CreatedTime = G.Max(p => p.CreatedTime)
}
on new { A = hps2.ProductID, B = hps2.CreatedTime } equals new { A = p.ProductId, B = p.CreatedTime }
select new
{
ProductId = hps2.ProductID,
Amount = hps2.Stock
}
on hp.id equals hs.ProductId
orderby hs.Amount
select new ProductDataAnalysisodel
{
ProductName = hp.ProductName,
ProductCode = hp.ProductCode,
Amount = hs.Amount.Value
}).Take();
pageModel.Models = data6.FindBy(item => true, productDataAnalysisQuery.PageNo, productDataAnalysisQuery.PageSize, out total, item => item.Amount, false); break;
}
Linq使用Group By
.简单形式: var q =
from p in db.Products
group p by p.CategoryID into g
select g;
语句描述:Linq使用Group By按CategoryID划分产品。 说明:from p in db.Products 表示从表中将产品对象取出来。group p by p.CategoryID into g表示对p按CategoryID字段归类。其结果命名为g,一旦重新命名,p的作用域就结束了,所以,最后select时,只能select g。 .最大值 var q =
from p in db.Products
group p by p.CategoryID into g
select new {
g.Key,
MaxPrice = g.Max(p => p.UnitPrice)
};
语句描述:Linq使用Group By和Max查找每个CategoryID的最高单价。 说明:先按CategoryID归类,判断各个分类产品中单价最大的Products。取出CategoryID值,并把UnitPrice值赋给MaxPrice。 .最小值 var q =
from p in db.Products
group p by p.CategoryID into g
select new {
g.Key,
MinPrice = g.Min(p => p.UnitPrice)
};
语句描述:Linq使用Group By和Min查找每个CategoryID的最低单价。 说明:先按CategoryID归类,判断各个分类产品中单价最小的Products。取出CategoryID值,并把UnitPrice值赋给MinPrice。 .平均值 var q =
from p in db.Products
group p by p.CategoryID into g
select new {
g.Key,
AveragePrice = g.Average(p => p.UnitPrice)
};
语句描述:Linq使用Group By和Average得到每个CategoryID的平均单价。 说明:先按CategoryID归类,取出CategoryID值和各个分类产品中单价的平均值。 .求和 var q =
from p in db.Products
group p by p.CategoryID into g
select new {
g.Key,
TotalPrice = g.Sum(p => p.UnitPrice)
};
今天遇到了一个问题,操作一个DataTable,DataTable的表结构如下:
- Id,Name,Math,Chinese
此表对应的数据如下图:
要求合并后的效果如下图:
自己就想到了for循环的实现办法,也想用Linq可是不知道怎么写。后来msdn了一下,写出了如下的代码:
var query = from c in ds.Tables[].AsEnumerable()
group c by c.Field<int>("Name")
into s
select new
{
ID = s.Select(m => m.Field<int>("ID").ToString()),
Name = s.Select(m => m.Field<string>("Name").ToString()),
Math = s.Sum(p => p.Field<decimal>("Math")),
Chinese = s.Sum(p => p.Field<decimal>("Chinese"))
}; //法一:
DataTable tbl = tableA1.Clone();
query.ToList().ForEach(p => tbl.Rows.Add(p.pingming, p.guige,p.biaohao,p.shuliang));
//法二:
DataTable dtss = new DataTable();
dtss.Columns.Add(new DataColumn("ID", typeof(string)));
dtss.Columns.Add(new DataColumn("Name", typeof(string)));
dtss.Columns.Add(new DataColumn("Math", typeof(string)));
dtss.Columns.Add(new DataColumn("Chinese", typeof(string)));
query.ToList().ForEach(p => dtss.Rows.Add(p.ID, p.Name, p.Math, p.Chinese ));
注意:linq结果可以用AsEnumerable立刻执行查询以及ToList ToArray转换成数组/集合
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