LINQ to SQL和订购的结果总运行 [英] LINQ to SQL and a running total on ordered results
问题描述
我想在 DataGridView的来显示客户的会计历史，我想有一个显示其资产负债运行总计列。旧的方式，我这样做是通过获取数据，通过数据的循环，并添加行到 DataGridView的一个接一个，计算当时的运行总计。瘸。我宁愿使用LINQ到SQL，或LINQ如果无法与LINQ到SQL，找出运行总计这样我就可以只设置 DataGridView.DataSource 我的数据。
这就是我拍摄的一个超级简单的例子。说我有下面的类。
类项目
{
公众的DateTime日期{搞定;组; }
公共小数金额{搞定;组; }
公共小数runningTotal在{搞定;组; }
}
我想一个L2S，或LINQ，报表可能产生的结果是这样的：
发行总额runningTotal在
12-01-2009 5
12-02-2009 -5 0
12-02-2009 10 10
2009年12月3日5月15日
2009年12月4日-15 0
注意，可以有多个项目具有相同的日期（12-02-2009）。结果应以日期计算的运行总计之前进行排序。我猜这意味着我需要两种说法，一是来获取数据和排序，并第二次执行运行总计计算。
我希望总结会做的伎俩，但它不喜欢工作，我希望。或者，也许我只是无法弄清楚。
似乎这问题，我想同样的事情后去，但我没有看到接受/只回答如何解决我的问题。
这是怎么拉这一关任何想法？
修改
梳理从亚历克斯和DOK的答案，这是我结束了：
小数runningTotal在= 0;
VAR的结果= FetchDataFromDatabase（）
.OrderBy（项目=＆GT; item.Date）
。选择（项目=＆gt;新建项目
{
金额= item.Amount，
日期= item.Date，
runningTotal在= runningTotal在+ = item.Amount
}）;
使用闭包和匿名的方式：
列表＆LT;项目＆GT; myList中= FetchDataFromDatabase（）;小数currentTotal = 0;
VAR的查询= myList中
.OrderBy（I =＆GT; i.Date）
。选择（I =＆GT;
{
currentTotal + = i.Amount;
返回新{
日期= i.Date，
金额= i.Amount，
runningTotal在= currentTotal
};
}
）;
的foreach（查询VAR项）
{
//做项目
}
I want to display a customer's accounting history in a DataGridView and I want to have a column that displays the running total for their balance. The old way I did this was by getting the data, looping through the data, and adding rows to the DataGridView one-by-one and calculating the running total at that time. Lame. I would much rather use LINQ to SQL, or LINQ if not possible with LINQ to SQL, to figure out the running totals so I can just set DataGridView.DataSource to my data.
This is a super-simplified example of what I'm shooting for. Say I have the following class.
class Item
{
public DateTime Date { get; set; }
public decimal Amount { get; set; }
public decimal RunningTotal { get; set; }
}
I would like a L2S, or LINQ, statement that could generate results that look like this:
Date Amount RunningTotal
12-01-2009 5 5
12-02-2009 -5 0
12-02-2009 10 10
12-03-2009 5 15
12-04-2009 -15 0
Notice that there can be multiple items with the same date (12-02-2009). The results should be sorted by date before the running totals are calculated. I'm guessing this means I'll need two statements, one to get the data and sort it and a second to perform the running total calculation.
I was hoping Aggregate would do the trick, but it doesn't work like I was hoping. Or maybe I just couldn't figure it out.
This question seemed to be going after the same thing I wanted, but I don't see how the accepted/only answer solves my problem.
Any ideas on how to pull this off?
Edit Combing the answers from Alex and DOK, this is what I ended up with:
decimal runningTotal = 0;
var results = FetchDataFromDatabase()
.OrderBy(item => item.Date)
.Select(item => new Item
{
Amount = item.Amount,
Date = item.Date,
RunningTotal = runningTotal += item.Amount
});
Using closures and anonymous method:
List<Item> myList = FetchDataFromDatabase();
decimal currentTotal = 0;
var query = myList
.OrderBy(i => i.Date)
.Select(i =>
{
currentTotal += i.Amount;
return new {
Date = i.Date,
Amount = i.Amount,
RunningTotal = currentTotal
};
}
);
foreach (var item in query)
{
//do with item
}
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