linq

问题 How could I do the join in linq from the following SQL SELECT statement by using method syntax : SELECT distinct [LAB_RESULTS].ORDER_ID ,LAB_RESULTS.patient_no ,Patients.PATIENT_NAME ,labtests.TestId ,labtests.TestName ,[RESULT_NUMBER] ,TestsRanges.LowerLimit ,TestsRanges.UpperLimit ,TestsUnits.UnitName FROM [dbo].[LAB_RESULTS] inner join LabTests on LabTests.testid=LAB_RESULTS.TESTID inner join TestsRanges on TestsRanges.TestId = LAB_RESULTS.TESTID inner join patients on Patients.Patient_No

问题 I'm having some doublts about concurrency using LINQ AsParallel() . Suppose I have the following code: int counter = 0; someList.AsParallel().ForEach(item => { doStuff(); counter++; }); I haven't found much online... Is it safe to do something like this? Is there a better way of doing this? Should I do some locking action for counter ? Thanks in advance 回答1: Is it safe to do something like this? ( counter++ ) No. There is no thread-safety to begin with, just code that is single-threaded. When

问题 I have a table, Items , which has a many to one relationship with two distinct parents. I want to select the counts of ParentA for each ParentB . In SQL this is simple: SELECT "ParentBId", count(distinct "ParentAId") FROM "Items" GROUP BY "ParentBId" In Linq I have this statement: var itemCounts = await _context.Items .GroupBy(item => item.ParentBId, (parentBId, items) => new { ParentBId = parentBId, Count = items.Select(item => item.ParentAId).Distinct().Count(), }).ToDictionaryAsync(group =

问题 I have an int[] array. I need to take an int and append it to the end of the array without affecting the position of the other items in that array. Using C# 4 and LINQ what is the most elegant way to achieve this? My Code: int[] items = activeList.Split(',').Select(n => Convert.ToInt32(n)).ToArray(); int itemToAdd = ddlDisabledTypes.SelectedValue.ToInt(0); // Need final list as a string string finalList = X Thanks for any help! 回答1: The easiest way is to change your expression around a bit.

问题 In C#, if I have a List of objects (e.g. List myObjectList), I can get a subset of that list via: anotherMyObjectList = myObjectList.Where(x => x.isSomething()).Select(x => x).ToList(); Assuming I don't want to use a 3rd party C++ LINQ library (only standard library and maybe boost), what's the best way to do this in C++? It would be easy to write a function for each instance where I want to do this, but it would be better to know what framework exists to perform this type of operation. If

问题 Hi I have a lookup type that stores strings and ints. static Lookup<string, int> lookup; lookup = (Lookup<string, int>)list.ToLookup(i => i.IP, i => i.Number); But now I need to sort this lookup by the values (number), and get the top 10 keys with their values. How is this possible? 回答1: I'm not sure why you are casting a Lookup<string, int> to a Lookup<string, string> , but the general answer you want is: var list = new List<Test> { new Test { IP = "A", Number = 1 }, new Test { IP = "A",

问题 Hi I have a lookup type that stores strings and ints. static Lookup<string, int> lookup; lookup = (Lookup<string, int>)list.ToLookup(i => i.IP, i => i.Number); But now I need to sort this lookup by the values (number), and get the top 10 keys with their values. How is this possible? 回答1: I'm not sure why you are casting a Lookup<string, int> to a Lookup<string, string> , but the general answer you want is: var list = new List<Test> { new Test { IP = "A", Number = 1 }, new Test { IP = "A",

问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 3 days ago . Improve this question Giving these classes in C# Inbox.cs public class Inbox : TDocument { public string Name {get;set;} public List<MongoDBRef> WorkOrdersRef {get;set;} public List<InboxRule> Rules {get;set;} [BsonIgnore] public List<WorkOrder> WorkOrders {get;set;} } InboxRule.cs

问题 I have a number of objects and each object has an array, I would like to group these objects by the values inside the array, so conceptually they look as follows: var objects = new []{ object1 = new object{ elements = []{1,2,3} }, object2 = new object{ elements = []{1,2} }, object3 = new object{ elements = []{1,2} }, object4 = new object{ elements = null } } after grouping: group1: object1 group2: object2,object3 group3: object4 somethings that I have tried: actual classes: public class

问题 I have a number of objects and each object has an array, I would like to group these objects by the values inside the array, so conceptually they look as follows: var objects = new []{ object1 = new object{ elements = []{1,2,3} }, object2 = new object{ elements = []{1,2} }, object3 = new object{ elements = []{1,2} }, object4 = new object{ elements = null } } after grouping: group1: object1 group2: object2,object3 group3: object4 somethings that I have tried: actual classes: public class