[英]Counting number of items in ObservableCollection where it equals 1 - C#
I made an SQL query and filled the data to an ObservableCollection. 我进行了SQL查询,并将数据填充到ObservableCollection中。 The database contains many columns so I want to count how many instances where a specific column = 1, then return that number to an int.
该数据库包含许多列,因此我想计算一个特定列= 1的实例数,然后将该数字返回给int。
The query: 查询:
var test = from x in m_dcSQL_Connection.Testheaders
where dtStartTime <= x.StartTime && dtEndtime >= x.StartTime
select new {
x.N,
x.StartTime,
x.TestTime,
x.TestStatus,
x.Operator,
x.Login,
x.DUT_id,
x.Tester_id,
x.PrintID
};
Then I add the data pulled from the database to an Observable Collection via: 然后,我通过以下方式将从数据库中提取的数据添加到Observable集合中:
lstTestData.Add(new clsTestNrData(item.N.ToString(),
item.StartTime.ToString(),
item.TestTime.ToString()
etc.....
I want to count how many times TestStatus = 1. 我想计算TestStatus = 1的次数。
I have read about the .Count property but I do not fully understand how it works on ObservableCollections. 我已经读过有关.Count属性的信息,但我还不完全了解它如何在ObservableCollections上工作。
Any help? 有什么帮助吗?
The standard ObservableCollection<T>.Count
property will give you the number of items in the collection. 标准的
ObservableCollection<T>.Count
属性将为您提供集合中的项目数。
What you are looking for is this: 您正在寻找的是:
testStatusOneItemCount = lstTestData.Where(item => item.TestStatus == 1).Count()
...which uses IEnumerable<T>.Count()
method which is part of LINQ. ...使用LINQ的
IEnumerable<T>.Count()
方法。
To elaborate a bit, Count
will simply count the objects in your collection. 为了详细说明,
Count
将仅对集合中的对象进行计数。
I suggest having a quick look at linq 101 . 我建议快速看一下linq 101 。 Very good examples.
很好的例子。
Here's an example: 这是一个例子:
// Assuming you have :
var list = new List<int>{1,2,3,4,5,6 };
var items_in_list = list.Count(); // = 6;
Using linq's Where
, you're basically filtering out items, creating a new list. 使用linq的
Where
,您基本上是在过滤项目,创建一个新列表。 So, the following will give you the count of all the numbers which are pair: 因此,以下将为您提供所有成对数字的计数:
var pair = list.Where(item => item%2 ==0);
var pair_count = pair.Count; // = 3
You can combine this without the temp variables: 您可以不使用temp变量将其组合:
var total = Enumerable.Range(1,6).Where(x => x % 2 ==0).Count(); // total = 6;
Or you can then select something else: 或者您可以选择其他内容:
var squares_of_pairs = Enumerable.Range(1,6)
.Where(x => x % 2 ==0).
.Select( pair => pair*pair);
// squares_of_pairs = {4,16, 36}. You can count them, but still get 3 :)
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