my question is simple but I got stuck with something. Can you tell me how can I reduce 2 select into 1 select LINQ in c#? I am using CloudNative.CloudEvents NuGet package for cloud-native events.
var orderEvents = input
.Select(_ => new OrderDocument(_.Id, _.ToString()).ToOrderEvent())
.Select(_ =>
new CloudEvent()
{
Type = _.EventType,
Subject = _.Subject,
Source = _.Source,
Data = _
});
input is a parameter from cosmosDbTrigger it`s type : IReadOnlyList
OrderDocument.cs
public class OrderDocument
{
public string Id { get; private set; }
public string Json { get; private set; }
public OrderDocument(string id, string json)
{
Id = id;
Json = json;
}
public OrderEvent ToOrderEvent() => OrderEventHelper.ToOrderEvent(Json);
}
OrderEventHelper.cs
public static OrderEvent ToOrderEvent(string json)
{
ArgumentHelper.ThrowIfNullOrEmpty(json);
var orderEvent = JsonConvert.DeserializeObject<OrderEvent>(json);
var eventDefinition = OrderEvents.EventDefinitions.SingleOrDefault(_ => _.EventType == orderEvent.EventType);
return eventDefinition == null
? orderEvent
: new OrderEvent(
orderEvent.Id,
orderEvent.Source,
orderEvent.EventType,
orderEvent.Subject,
orderEvent.DataContentType,
orderEvent.DataSchema,
orderEvent.Timestamp,
JsonConvert.DeserializeObject(orderEvent.Payload.ToString(), eventDefinition.PayloadType),
orderEvent.TraceId);
}
linq extensions are basically for loops in the background. If you want to perform multiple actions against a list, perhaps making your own simple for loop where you can manage that yourself would work.
Your code:
var orderEvents = input
.Select(_ => new OrderDocument(_.Id, _.ToString()).ToOrderEvent())
.Select(_ =>
new CloudEvent()
{
Type = _.EventType,
Subject = _.Subject,
Source = _.Source,
Data = _
});
could be changed to:
// our result set, rather than the one returned from linq Select
var results = new List<CloudEvent>();
foreach(var x in input){
// create the order event here
var temporaryOrderEvent = new OrderDocument(x.Id, x.ToString()).ToOrderEvent();
// add the Cloud event to our result set
results.Add(new CloudEvent()
{
Type = temporaryOrderEvent .EventType,
Subject = temporaryOrderEvent .Subject,
Source = temporaryOrderEvent .Source,
Data = temporaryOrderEvent
});
}
where you then have a result list to work with.
If you wanted to keep it all in linq, you could instead perform all of your logic in the first Select, and ensure that it returns a CloudEvent. Notice here that you can employ the use of curly brackets in the linq statement to evaluate a function rather than a single variable value:
var orderEvents = input
.Select(x =>
{
// create the order event here
var temporaryOrderEvent = new OrderDocument(x.Id, x.ToString()).ToOrderEvent();
// return the Cloud event here
return new CloudEvent()
{
Type = temporaryOrderEvent .EventType,
Subject = temporaryOrderEvent .Subject,
Source = temporaryOrderEvent .Source,
Data = temporaryOrderEvent
};
});
How about putting conversion to OrderEvent and using ToCloudEvent in the same Select?
var orderEvents = input
.Select(_ => new OrderDocument(_.Id, _.ToString()).ToOrderEvent().ToCloudEvent())
public class OrderEvent
{
public CloudEvent ToCloudEvent()
{
new CloudEvent()
{
Type = this.EventType,
Subject = this.Subject,
Source = this.Source,
Data = this
};
}
}
Related
I cannot seem to get the desirable filtered result from my query.
Data
public class fdp_1115
{
public string Id{ get; set; }
public string Number{ get; set; }
public string Type{ get; set; }
}
List<fdp_1115> fdpList = new List<fdp_1115>
{
new fdp_1115 { Id = "1", Number = "Lot123", Type = "D14MWT" },
new fdp_1115 { Id = "2", Number = "Lot123", Type = "E12WBC7W1" }
};
List<string> searchValues = new List<string> { "MLE12WBC7W1 A R" };
LINQ:
var LocType = fdpList.FirstOrDefault(d => searchValues.Any(s => d.Type.Contains(s)));
if (LocType != null)
{
Console.WriteLine("Matching record found:");
Console.WriteLine($"Id: {LocType.Id}, Number: {LocType.Number}, Type: {LocType.Type}");
}
else
{
Console.WriteLine("No matching records found.");
}
The result I wanted is:
Matching record found:
Id: 2, Number: Lot123, Type: E12WBC7W1
But I got "No matching records found." which indicates that LocType == null.
I already tried trimming and ignoring case sensitive:
var LocType = fdpList.FirstOrDefault(d => searchValues.Any(s => d.Type.Contains(s.Trim().Replace(" ", ""))));
var LocType = fdpList.FirstOrDefault(d => searchValues.Any(s => d.Type.Contains(s, StringComparison.InvariantCultureIgnoreCase)));
But still no luck. Any idea how do I match "MLE12WBC7W1 A R" with "E12WBC7W1"?
You have your contains the other way around.
d.Type = "E12WBC7W1"
and
s = "MLE12WBC7W1 A R"
Then "E12WBC7W1" does not Contains "MLE12WBC7W1 A R"
It is the other way around.
var LocType = fdpList.FirstOrDefault(d => searchValues.Any(s => s.Contains(d.Type)));
Your current logic checks whether there is any object with Type value that contains the value for each string in the searchValues array.
From your requirement:
You want to filter the object that fulfills there is any string in searchValues containing the value of Type.
Thus it should be:
var LocType = fdpList.FirstOrDefault(d => searchValues.Any(s => s.Contains(d.Type)));
I have Linq script and I want to use projection class to get data to DTO type. I got the example for lambda expersion but getting error on the LINQ script.
Linq Script:
public class EziTransactionDto
{
... other properties
public static Expression<Func<EziTransactionEntity, EziTransactionDto>> Projection()
{
return eziTransactionDto => new EziTransactionDto
{
EziTransactionId = eziTransactionDto.Id,
LoginSiteID = eziTransactionDto.LoginSiteID,
WorkCodes = eziTransactionDto.WorkCodes
};
}
Linq query:
var ts = (from transaction in _eziTransactionRepository.GetAll<EziTransactionEntity>()
where transaction.LoginErrorCode != 0
select transaction
).Select(EziTransactionDto.Projection);
Error:
I guess the keyword Expression is odd there.
Try this:
// public static Expression<Func<EziTransactionEntity, EziTransactionDto>> Projection()
public static Func<EziTransactionEntity, EziTransactionDto> Projection()
{
return eziTransactionDto => new EziTransactionDto
{
EziTransactionId = eziTransactionDto.Id,
LoginSiteID = eziTransactionDto.LoginSiteID,
WorkCodes = eziTransactionDto.WorkCodes
};
}
After the first Select your IQueryable has already fetched the data to the local process, and made it an IEnumerable.
You could do this conversion in your Select statement:
var eziTransactionDtos = _eziTransactionRepository.EziTransactionEntities
.Where(eziTransactionEntity => eziTransationEntity.LoginErrorCode != 0)
.Select(eziTransactionEntity => new EziTransactionDto
{
EziTransactionId = eziTransactionDto.Id,
LoginSiteID = eziTransactionDto.LoginSiteID,
WorkCodes = eziTransactionDto.WorkCodes,
});
However, if you need to convert EziTransactionEntities to EziTransactionDtos on several places, it is a good idea to create a reusable extension method for IQueryable<EziTransactionEntities>.
If you are not familiar with extension methods, see extension methods demystified
public static IQueryable<EziTransactionDto> ToEziTransactionDto(
this IQueryable<EziTransactionEntity> eziTransactionEntities)
{
return eziTransactionEntities.Select(eziTransactionEntity => new EziTransactionDto
{
EziTransactionId = eziTransactionDto.Id,
LoginSiteID = eziTransactionDto.LoginSiteID,
WorkCodes = eziTransactionDto.WorkCodes,
});
Usage:
var eziTransactionDtos = eziTransactionRepository.EziTransactionEntities
.Where(eziTransactionEntity => eziTransationEntity.LoginErrorCode != 0)
.ToEziTransactionDtos();
Reusable:
var transactionWithoutWorkCodes = eziTransactionRepository.EziTransactionEntities
.Where(eziTransactionEntity => eziTransationEntity.WorkCode == null)
.ToEziTransactionDtos();
Easy to unit test:
List<EziTransactionEntity> testItems = ...
List<EziTransactionDto> expectedResults = ...
var testResults = testItems.AsQueryable().ToEziTransactionDtos();
Assert.AreQual(expectedResults, testResults, unorderedTransactionsComparer);
Easy to maintain: if you add / remove / change one property of this conversion, you'll only have to do this on one location
fond the answer
public static Expression<Func<EziTransactionEntity, EziTransactionDto>> Projection
{
get
{
return eziTransactionDto => new EziTransactionDto
{
EziTransactionId = eziTransactionDto.Id,
LoginSiteID = eziTransactionDto.LoginSiteID,
WorkCodes = eziTransactionDto.WorkCodes
};
}
}
..
var ts = (from transaction in _eziTransactionRepository.GetAll<EziTransactionEntity>()
select transaction
).Select(EziTransactionDto.Projection).ToList();
My code already gets the table without containing a string. How can I get a list without containing a list of strings? I want to get the result of SELECT * FROM table WHERE column NOT IN ('x' ,'y');
public IEnumerable<keyart1> Get(string keyword)
{
List<keyart1> keylist;
using (dbEntities5 entities = new dbEntities5())
{
keylist = entities.keyart1.Where(e => e.keyword != keyword).ToList();
var result = keylist.Distinct(new ItemEqualityComparer());
return result;
}
}
I think i found the answer if anybody interested
public IEnumerable<keyart1> Get([FromUri] string[] keyword1)
{
List<keyart1> keylist;
List<IEnumerable<keyart1>> ll;
using (dbEntities5 entities = new dbEntities5())
{
ll = new List<IEnumerable<keyart1>>();
foreach (var item in keyword1)
{
keylist = entities.keyart1.Where(e => e.keyword != item).ToList();
var result = keylist.Distinct(new ItemEqualityComparer());
ll.Add(result);
}
var intersection = ll.Aggregate((p, n) => p.Intersect(n).ToList());
return intersection;
}
}
I have seen multiple questions that are similar to this one but I think my case is slightly different. I'm using EF6 to query the database and I'm using data projection for better queries.
Given that performance is very important on this project I have to make sure to just read the actual fields that I will use so I have very similar queries that are different for just a few fields as I have done this I have noticed repetition of the code so I'm been thinking on how to reuse code this is currently what I Have:
public static IEnumerable<FundWithReturns> GetSimpleFunds(this DbSet<Fund> funds, IEnumerable<int> fundsId)
{
IQueryable<Fund> query = GetFundsQuery(funds, fundsId);
var results = query
.Select(f => new FundWithReturns
{
Category = f.Category,
ExpenseRatio = f.ExpenseRatio,
FundId = f.FundId,
Name = f.Name,
LatestPrice = f.LatestPrice,
DailyReturns = f.FundDailyReturns
.Where(dr => dr.AdjustedValue != null)
.OrderByDescending(dr => dr.CloseDate)
.Select(dr => new DailyReturnPrice
{
CloseDate = dr.CloseDate,
Value = dr.AdjustedValue.Value,
}),
Returns = f.Returns.Select(r => new ReturnValues
{
Daily = r.AdjDaily,
FiveYear = r.AdjFiveYear,
MTD = r.AdjMTD,
OneYear = r.AdjOneYear,
QTD = r.AdjQTD,
SixMonth = r.AdjSixMonth,
ThreeYear = r.AdjThreeYear,
YTD = r.AdjYTD
}).FirstOrDefault()
})
.ToList();
foreach (var result in results)
{
result.DailyReturns = result.DailyReturns.ConvertClosingPricesToDailyReturns();
}
return results;
}
public static IEnumerable<FundListVm> GetFundListVm(this DbSet<Fund> funds, string type)
{
return funds
.Where(f => f.StatusCode == MetisDataObjectStatusCodes.ACTIVE
&& f.Type == type)
.Select(f => new FundListVm
{
Category = f.Category,
Name = f.Name,
Symbol = f.Symbol,
Yield = f.Yield,
ExpenseRatio = f.ExpenseRatio,
LatestDate = f.LatestDate,
Returns = f.Returns.Select(r => new ReturnValues
{
Daily = r.AdjDaily,
FiveYear = r.AdjFiveYear,
MTD = r.AdjMTD,
OneYear = r.AdjOneYear,
QTD = r.AdjQTD,
SixMonth = r.AdjSixMonth,
ThreeYear = r.AdjThreeYear,
YTD = r.AdjYTD
}).FirstOrDefault()
}).OrderBy(f=>f.Symbol).Take(30).ToList();
}
I'm trying to reuse the part where I map the f.Returns so I tried created a Func<> like the following:
private static Func<Return, ReturnValues> MapToReturnValues = r => new ReturnValues
{
Daily = r.AdjDaily,
FiveYear = r.AdjFiveYear,
MTD = r.AdjMTD,
OneYear = r.AdjOneYear,
QTD = r.AdjQTD,
SixMonth = r.AdjSixMonth,
ThreeYear = r.AdjThreeYear,
YTD = r.AdjYTD
};
and then use like this:
public static IEnumerable<FundListVm> GetFundListVm(this DbSet<Fund> funds, string type)
{
return funds
.Where(f => f.StatusCode == MetisDataObjectStatusCodes.ACTIVE
&& f.Type == type)
.Select(f => new FundListVm
{
Category = f.Category,
Name = f.Name,
Symbol = f.Symbol,
Yield = f.Yield,
ExpenseRatio = f.ExpenseRatio,
LatestDate = f.LatestDate,
Returns = f.Returns.Select(MapToReturnValues).FirstOrDefault()
}).OrderBy(f=>f.Symbol).Take(30).ToList();
}
The compiler is ok with it but at runtime, it crashes and says: Internal .NET Framework Data Provider error 1025
I tried to convert the Func into Expression like I read on some questions and then using compile() but It didn't work using AsEnumerable is also not an option because It will query all the fields first which is what I want to avoid.
Am I trying something not possible?
Thank you for your time.
It definitely needs to be Expression<Func<...>>. But instead of using Compile() method (not supported), you can resolve the compile time error using the AsQueryable() method which is perfectly supported (in EF6, the trick doesn't work in current EF Core).
Given the modified definition
private static Expression<Func<Return, ReturnValues>> MapToReturnValues =
r => new ReturnValues { ... };
the sample usage would be
Returns = f.Returns.AsQueryable().Select(MapToReturnValues).FirstOrDefault()
I have this code:
List<MyObjectOne> myListOne = new List<MyObjectOne>(){new MyObjectOne { ID = 1, field2 = 2}};
List<MyObjectTwo> myListTwo = new List<MyObjectTwo>(){new MyObjectTwo { ID = 4, field6 = "string"}};
bool hasSomething = false;
var result = new[] { new {ID = 0 }}.ToList();
if (hasSomething)
{
// Use list one.
result = myListOne.Select(x => new { ID = x.ID});
}
else
{
// Use list two.
result = myListTwo.Select(x => new { ID = x.ID });
}
foreach (var item in result)
{
// Some logic to manipulate item.ID.
item.ID;
}
What I trying to do it's to use the same anonymous type to select a list of IDs from two different lists. So I use the Select(x => new { ID = x.ID }) in order to create the anonymous type for each table in order to have only one for loop.
The error raised is "Cannot implicitly convert type IEnumerable to List"
¿any idea?
Assuming ID in MyObjectOne and MyObjectTwo are both int's, your code will work if you replace ToList with AsEnumerable:
var result = new[] { new { ID = 0 } }.AsEnumerable();
If the ID properties are some other type (e.g. long's), you need to specify that when creating the anonymous type here:
var result = new[] { new { ID = 0L } }.AsEnumerable();
Or like this:
var result = new[] { new { ID = (long)0 } }.AsEnumerable();
However, this kind of code is kind of confusing, and I wouldn't recommend it for a production environment. Here's an alternative solution that avoids creating a 'dummy' object just for implicit anonymous typing:
var result = hasSomething
? myListOne.Select(x => new { ID = x.ID })
: myListTwo.Select(x => new { ID = x.ID });