Develop Reference

How to yield multiple objects with respect to a multi-valued column in Dynamic Linq

Scenario:
I have to export an excel file which will contain list of Parts. We have enabled the user to select the columns and get only selected columns' data in the exported file. Since this is a dynamic report, I am not using any concrete class to map the report as this will result in exporting empty column headers in the report, which is unnecessary. I am using Dynamic Linq to deal with this scenario.
I have a list of dynamic objects fetched from dynamic linq.
[
{"CleanPartNo":"Test","Description":"test","AliasPartNo":["258","145","2313","12322"]},
{"CleanPartNo":"Test1","Description":"test1","AliasPartNo":[]}
]
How can I get 4 rows out of this json like
Please note that I cannot use a strongly typed object to deserialize/ Map it using JSON.Net
Update
Following is the code:
public class Part
{
public int Id { get; set; }
public string CleanPartNo { get; set; }
public string Description { get; set; }
public List<PartAlias> AliasPartNo { get; set; }
}
public class PartAlias
{
public int PartId { get; set; }
public int PartAliasId { get; set; }
public string AliasPartNo { get; set; }
}
var aliases = new List<PartAlias> {
new PartAlias{AliasPartNo="258" },
new PartAlias{AliasPartNo="145" },
new PartAlias{AliasPartNo="2313" },
new PartAlias{AliasPartNo="12322" }
};
List<Part> results = new List<Part> {
new Part{CleanPartNo="Test", Description= "test", PartAlias=aliases },
new Part{CleanPartNo="Test1", Description= "test1" }
};
var filters = "CleanPartNo,Description, PartAlias.Select(AliasPartNo) as AliasPartNo";
var dynamicObject = JsonConvert.SerializeObject(results.AsQueryable().Select($"new ({filters})"));
in the dynamicObject variable I get the json mentioned above

Disclaimer: The following relies on anonymous classes, which is not exactly the same as dynamic LINQ (not at all), but I figured that it may help anyway, depending on your needs, hence I decided to post it.
To flatten your list, you could go with a nested Select, followed by a SelectMany (Disclaimer: This assumes that every part has at least one alias, see below for the full code)
var flattenedResult = result.Select(part => part.AliasPartNumber.Select(alias => new
{
CleanPartNo = part.CleanPartNo,
Description = part.Description,
AliasPartNo = alias.AliasPartNo
})
.SelectMany(part => part);
You are first projecting your items from result (outer Select). The projection projects each item to an IEnumerable of an anonymous type in which each item corresponds to an alias part number. Since the outer Select will yield an IEnumerable<IEnumerable> (or omething alike), we are using SelectMany to get a single IEnumerable of all the items from your nested IEnumerables. You can now serialize this IEnumerable of instances of an anonymous class with JsonConvert
var json = sonConvert.SerializeObject(flatResults);
Handling parts without aliases
If there are no aliases, the inner select will yield an empty IEnumerable, hence we will have to introduce a special case
var selector = (Part part) => part.AliasPartNumber?.Any() == true
? part.AliasPartNumber.Select(alias => new
{
CleanPartNo = part.CleanPartNo,
Description = part.Description,
AliasPartNo = alias.AliasPartNo
})
: new[]
{
new
{
CleanPartNo = part.CleanPartNo,
Description = part.Description,
AliasPartNo = alias.AliasPartNo
}
};
var flattenedResult = result.Select(selector).SelectMany(item => item);

From json you provided you can get values grouped by their name in this way:
var array = JArray.Parse(json);
var lookup = array.SelectMany(x => x.Children<JProperty>()).ToLookup(x => x.Name, x => x.Value);
then this is just a manner of simple loop over the lookup to fill the excel columns.
However, I would suggest to do the flatenning before JSON. I tried for some time to make it happen even without knowing the names of the columns that are arrays, but I failed, and since it's your job, I won't try anymore :P
I think the best way here would be to implement custom converter that would just multiply objects for properties that are arrays. If you do it well, you would get infinite levels completely for free.

Looping header and details records in same file

I have re edit this question below I have an example file which as multiple purchase orders in the file which is identified by the second column.
Order Number, Purchase Number,DATE,Item Code ,Qty, Description
1245456,98978,12/01/2019, 1545-878, 1,"Test"
1245456,98978,12/01/2019,1545-342,2,"Test"
1245456,98978,12/01/2019,1545-878,2,"Test"
1245456,98979,12/02/2019,1545-878,3,"Test 3"
1245456,98979,12/02/2019,1545-342,4,"Test 4"
1245456,98979,12/02/2019,1545-878,5,"Test 4"
What I want the end result to be is to be able to place the above into one class like the following
At the min I am using filelpers to parse the csv file this would work fine if I had sep header file and row file but they are combined as you see
var engine = new FileHelperEngine<CSVLines>();
var lines = engine.ReadFile(csvFileName);
So the Class should be like below
[DelimitedRecord(",")]
public class SalesOrderHeader
{
private Guid? _guid;
public Guid RowID
{
get
{
return _guid ?? (_guid = Guid.NewGuid()).GetValueOrDefault();
}
}
public string DocReference { get; set; }
public string CardCode { get; set; }
public string DocDate { get; set; }
public string ItemCode { get; set; }
public string Description { get; set; }
public string Qty { get; set; }
public string Price { get; set; }
[FieldHidden]
public List<SalesOrderHeader> OrdersLines { get; set; }
}
What I imagine I will have to do is two loops as you will see from my createsales order routine i first create the header and then add the lines in.
public void CreateSalesOrder(List<SalesOrderHeader> _salesOrders)
{
foreach (var record in _salesOrders.GroupBy(g => g.DocReference))
{
// Init the Order object
oOrder = (SAPbobsCOM.Documents)company.GetBusinessObject(SAPbobsCOM.BoObjectTypes.oOrders);
SAPbobsCOM.SBObob oBob;
// set properties of the Order object
// oOrder.NumAtCard = record.Where(w=>w.RowID = record.Where()
oOrder.CardCode = record.First().CardCode;
oOrder.DocDueDate = DateTime.Now;
oOrder.DocDate =Convert.ToDateTime(record.First().DocDate);
foreach (var recordItems in _salesOrders.SelectMany(e=>e.OrdersLines).Where(w=>w.DocReference ==record.First().DocReference))
{
oOrder.Lines.ItemCode = recordItems.ItemCode;
oOrder.Lines.ItemDescription = recordItems.Description;
oOrder.Lines.Quantity = Convert.ToDouble(recordItems.Qty);
oOrder.Lines.Price = Convert.ToDouble(recordItems.Price);
oOrder.Lines.Add();
log.Debug(string.Format("Order Line added to sap Item Code={0}, Description={1},Qty={2}", recordItems.ItemCode, recordItems.Description, recordItems.Qty));
}
int lRetCode = oOrder.Add(); // Try to add the orer to the database
}
if(lRetCode == 0)
{
string body = "Purchase Order Imported into SAP";
}
if (lRetCode != 0)
{
int temp_int = lErrCode;
string temp_string = sErrMsg;
company.GetLastError(out temp_int, out temp_string);
if (lErrCode != -4006) // Incase adding an order failed
{
log.Error(string.Format("Error adding an order into sap ErrorCode {0},{1}", temp_int, temp_string));
}
}
}
The problem you will see i have is how do I first split the csv into the two lists and second how do i access the header rows correctly in the strongly type object as you see I am using first which will not work correctly.

With FileHelpers it is important to avoid using the mapping class for anything other than describing the underlying file structure. Here I suspect you are trying to map directly to a class which is too complex.
A FileHelpers class is just a way of defining the specification of a flat file using C# syntax.
As such, the FileHelpers classes are an unusual type of C# class and you should not try to use accepted OOP principles. FileHelpers should not have properties or methods beyond the ones used by the FileHelpers library.
Think of the FileHelpers class as the 'specification' of your CSV format only. That should be its only role. (This is good practice from a maintenance perspective anyway - if the underlying CSV structure were to change, it is easier to adapt your code).
Then if you need the records in a more 'normal' object, then map the results to something better, that is, a class that encapsulates all the functionality of the Order object rather than the CSVOrder.
So, one way of handling this type of file is to parse the file twice. In the first pass you extract the header records. Something like this:
var engine1 = new FileHelperEngine<CSVHeaders>();
var headers = engine1.ReadFile(csvFileName);
In the second pass you extract the details;
var engine2 = new FileHelperEngine<CSVDetails>();
var details = engine2.ReadFile(csvFileName);
Then you combine this information into a new dedicated class, maybe with some LINQ similar to this
var niceOrders =
headers
.DistinctBy(h => h.OrderNumber)
.SelectMany(d => details.Where(d => d.OrderNumber = y))
.Select(x =>
new NiceOrder() {
OrderNumber = x.OrderNumber,
Customer = x.Customer,
ItemCode = x.ItemCode
// etc.
});

MongoDB Linq OfType() on fields

This is my MongoDB document structure:
{
string _id;
ObservableCollection<DataElement> PartData;
ObservableCollection<DataElement> SensorData;
...
other ObservableCollection<DataElement> fields
...
other types and fields
...
}
Is there any possibility to retrieve a concatenation of fields with the type ObservableCollection<DataElement>? Using LINQ I would do something like
var query = dbCollection
.AsQueryable()
.Select(x => new {
data = x
.OfType(typeof(ObservableCollection<DataElement>))
.SelectMany(x => x)
.ToList()
});
or alternatively
data = x.Where(y => typeof(y) == typeof(ObservableCollection<DataElement>)
.SelectMany(x => x).ToList()
Unfortunately .Where() and .OfType() do not work on documents, only on queryables/lists, so is there another possibility to achieve this? The document structure must stay the same.
Edit:
After dnickless answer I tried it with method 1b), which works pretty well for getting the fields thy way they are in the collection. Thank you!
Unfortunately it wasn't precisely what I was looking for, as I wanted to be all those fields with that specific type put together in one List, at it would be returned by the OfType or Where(typeof) statement.
e.g. data = [x.PartData , x.SensorData, ...] with data being an ObsverableCollection<DataElement>[], so that I can use SelectMany() on that to finally get the concatenation of all sequences.
Sorry for asking the question unprecisely and not including the last step of doing a SelectMany()/Concat()
Finally I found a solution doing this, but it doesn't seem very elegant to me, as it needs one concat() for every element (and I have more of them) and it needs to make a new collection when finding a non-existing field:
query.Select(x => new
{
part = x.PartData ?? new ObservableCollection<DataElement>(),
sensor = x.SensorData ?? new ObservableCollection<DataElement>(),
}
)
.Select(x => new
{
dataElements = x.part.Concat(x.sensor)
}
).ToList()

In order to limit the fields returned you would need to use the MongoDB Projection feature in one way or the other.
There's a few alternatives depending on your specific requirements that I can think of:
Option 1a (fairly static approach): Create a custom type with only the fields that you are interested in if you know them upfront. Something like this:
public class OnlyWhatWeAreInterestedIn
{
public ObservableCollection<DataElement> PartData { get; set; }
public ObservableCollection<DataElement> SensorData { get; set; }
// ...
}
Then you can query your Collection like that:
var collection = new MongoClient().GetDatabase("test").GetCollection<OnlyWhatWeAreInterestedIn>("test");
var result = collection.Find(FilterDefinition<OnlyWhatWeAreInterestedIn>.Empty);
Using this approach you get a nicely typed result back without the need for custom projections.
Option 1b (still pretty static): A minor variation of Option 1a, just without a new explicit type but a projection stage instead to limit the returned fields. Kind of like that:
var collection = new MongoClient().GetDatabase("test").GetCollection<Test>("test");
var result = collection.Find(FilterDefinition<Test>.Empty).Project(t => new { t.PartData, t.SensorData }).ToList();
Again, you get a nicely typed C# entity back that you can continue to operate on.
Option 2: Use some dark reflection magic in order to dynamically create a projection stage. Downside: You won't get a typed instance reflecting your properties but instead a BsonDocument so you will have to deal with that afterwards. Also, if you have any custom MongoDB mappings in place, you would need to add some code to deal with them.
Here's the full example code:
First, your entities:
public class Test
{
string _id;
public ObservableCollection<DataElement> PartData { get; set; }
public ObservableCollection<DataElement> SensorData { get; set; }
// just to have one additional property that will not be part of the returned document
public string TestString { get; set; }
}
public class DataElement
{
}
And then the test program:
public class Program
{
static void Main(string[] args)
{
var collection = new MongoClient().GetDatabase("test").GetCollection<Test>("test");
// insert test record
collection.InsertOne(
new Test
{
PartData = new ObservableCollection<DataElement>(
new ObservableCollection<DataElement>
{
new DataElement(),
new DataElement()
}),
SensorData = new ObservableCollection<DataElement>(
new ObservableCollection<DataElement>
{
new DataElement(),
new DataElement()
}),
TestString = "SomeString"
});
// here, we use reflection to find the relevant properties
var allPropertiesThatWeAreLookingFor = typeof(Test).GetProperties().Where(p => typeof(ObservableCollection<DataElement>).IsAssignableFrom(p.PropertyType));
// create a string of all properties that we are interested in with a ":1" appended so MongoDB will return these fields only
// in our example, this will look like
// "PartData:1,SensorData:1"
var mongoDbProjection = string.Join(",", allPropertiesThatWeAreLookingFor.Select(p => $"{p.Name}:1"));
// we do not want MongoDB to return the _id field because it's not of the selected type but would be returned by default otherwise
mongoDbProjection += ",_id:0";
var result = collection.Find(FilterDefinition<Test>.Empty).Project($"{{{mongoDbProjection}}}").ToList();
Console.ReadLine();
}
}

LinQ to view in MVC

In my controller I have a method that looks like this:
var CarModelAndGear = from search in entity.CarsCategories
where search.ID == CarCategoryId[0]
select new { search.Manufacturer, search.Model, search.Gear };
I'm trying to get the output of this statement to the view..
ViewData["somename"] = CarModelAndGear;
This way won't work.. I'm getting an error "LINQ to entities does not recognize the method 'Int32 get_Item(Int32)' method, and this method cannot be translated into a store expression. "
How can I get 'CarModelAndGear' to the view?

You need to store the category in a variable first because the provider is not able to interpret the list indexer method:
int CatId = CarCategoryId[0];
var CarModelAndGear = from search in entity.CarsCategories
where search.ID == CatId
select new { search.Manufacturer, search.Model, search.Gear };

You are using LinqToSql here. So what it is trying to do is convert that Linq expression into a SQL statement.
While you can access an item in a collection from C#, this cannot be translated into SQL, so it falls over.
Try this rather:
var id = CarCategoryId[0];
var CarModelAndGear = from search in entity.CarsCategories
where search.ID == id
select new { search.Manufacturer, search.Model, search.Gear };

You can execute linq and then assign to ViewData
ViewData["somename"] = CarModelAndGear.ToList();
But i prefer approach described by live2, when you will combine everything to model and then pass the model

Create a model for your result
public class CarViewResult
{
public string Manufacturer { get; set; }
public string Model { get; set; }
public string Gear { get; set; }
public CarViewResult(string manufacturer, string model, string gear)
{
this.Manufacturer = manufacturer;
this.Model = model;
this.Gear = gear;
}
}
Add add the new model to your LINQ query
var CarModelAndGear = from search in entity.CarsCategories
where search.ID == CarCategoryId[0]
select new CarViewResult(search.Manufacturer, search.Model, search.Gear);
ViewData["somename"] = CarModelAndGear.ToList();

How to Cast List<T> To List<ClassName>

I am using generic method to fill my dropdown for all types
below is my code.
the entity type are as follow
public class Role
{
public string Id { get; set; }
public string Name { get; set; }
}
public class DropDown
{
public string Id { get; set; }
public string Name { get; set; }
}
i am able to fetch data successfully at
var data = DataFetcher.FetchData<T>();
private static void Main( string[] args )
{
List<DropDown> cities = BLL.GetDataList<City>();
List<DropDown> states = BLL.GetDataList<State>();
List<DropDown> roles = BLL.GetDataList<Role>();
}
public static class BLL
{
public static List<DropDown> GetDataList<T>() where T : class ,new()
{
var data = DataFetcher.FetchData<T>();
return data as List<DropDown>;
}
}
I knew this cast data as List<DropDown> will fail,thats why its returning null back to calling method,
How can i cast Generic list to List of Known Type?

You have to ask yourself: how do I want to convert T to DropDown? If you can't answer this, the answer is: you can't.
I guess your DropDown class has an object Value property, that holds the dropdown value, and you wish to assign the data entity to that property.
Then you can project the list of data entities to DropDowns as such:
var data = DataFetcher.FetchData<T>();
return data.Select(d => new DropDown { Value = d }).ToList();
As for your edit: so you have at least one type, the displayed Role, that has an Id and Name property. But type T doesn't guarantee this, so you'd need to introduce an interface:
public interface INamedIdentifyableEntity
{
string Id { get; set; }
string Name { get; set; }
}
And apply this to your entities. Then introduce it as a generic constraint and do the mapping:
return data.Select(d => new DropDown
{
Id = d.Id,
Name = d.Name,
}).ToList();
But you don't want this, as here you are tying these two properties to dropdowns. Tomorrow you'll want an entity with Code instead of Id and Text instead of Name, so you'll have to add more interfaces, more overloads, and so on.
Instead you might want to use reflection, where you can specify the member names in the call:
List<DropDown> cities = BLL.GetDataList<City>(valueMember: c => c.CityCode, displayMember: c => c.FullCityname);
And use these member expressions to look up data's values and fill those into the DropDown.
However, you're then reinventing the wheel. Leave out your DropDown class entirely, and leave the dropdown generation to the front end, in this case MVC:
var cities = DataFetcher.FetchData<City>();
var selectList = new SelectList(cities.Select(c => new SelectListItem
{
Selected = (c.Id == selectedCityId),
Text = c.FullCityName,
Value = c.CityCode,
});
Or:
var selectList = new SelectList(cities, "CityCode" , "FullCityName", selectedCityId);

One solution is to use AutoMapper.
First create a map between your models like this:
AutoMapper.Mapper.CreateMap<Role, DropDown>();
Do the same thing for City and State classes if you need to.
Then you can use AutpMapper to convert your objects to DropDown like this:
public static List<DropDown> GetDataList<T>() where T : class ,new()
{
var data = DataFetcher.FetchData<T>();
return data.Select(x => AutoMapper.Mapper.Map<DropDown>(x)).ToList();
}

If I understood the question correctly, you could use Linq as follows.
return data.Cast<DropDown>().ToList();