i have code like this :
var list = _appData.GetAdvanceSearchData(Convert.ToInt16(collection["Product"])).ToList();
List<ProductMaterial> materials = list.Select(x => x.ProductMaterial).Distinct().ToList();
Exception I got :
Cannot implicitly convert type 'System.Collections.Generic.List<string>' to 'System.Collections.Generic.List<Crescent.LinqModel.ProductMaterial>'
whst should be done ?
Product Material Class :
public class ProductMaterial
{
public string ProductMaterials {get;set;}
}
list.Select(x => x.ProductMaterial).Distinct().ToList() gives me array string though have converted to list , i want the result of type 'ProductMaterial'.
Use this instead:
var materials = list.Select(x => x.ProductMaterial).Distinct().ToList();
Or:
List<string> materials = list.Select(x => x.ProductMaterial).Distinct().ToList();
The only thing that is different is the type of the materials variable.
I guess you want DistinctBy
List<ProductMaterial> materials =
list.DistinctBy(x => x.ProductMaterial).ToList();
You can use that extension method or search for some other implementation here
The query list.Select(x => x.ProductMaterial).Distinct().ToList(); returns List<string> not List<ProductMaterial>.
You can use List instead of List<ProductMaterial>.
I am not sure about what you want.I could have given a more precise opinion if data type of list was specified.
Related
This question already has answers here:
Case insensitive 'Contains(string)'
(29 answers)
Closed 2 years ago.
I am sorting a list of elements:
var matchEle = listOfElements.Where(e => e.Properties().Any(p => p.Name.Contains("Key", Asking for IEqualityComparer))).First();
I am used to just going straight to a StringComparer, OrdinalIgnoreCase or CurrentCultureIgnoreCase, however when calling Contains() in this context, it is asking for an IEqualityComparer. I imagine because of the data structure/level. I saw an example of how to set up an IEqualityComparer such as
strEqualityComparer = new IEqualityComparer();
and defining the class for strEqualityComparer but I am not sure beyond that. Can someone help me get my linq statement to work with an ignore case?
Update:
Just so I'm clear here is an example of the data structure:
listOfElements = [element1, element2, etc..]
element1.Properties = ["Prop1", "Key1", "Prop2", "Key2", etc.]
I need to extract the elements which pass the filter if any of its properties has a value containing the keyword, in this case "Key" therefore it cannot be .Equals or IndexOf.
Update as per comment
Search string inside another string:
var matchEle = listOfElements
.Where(e => e.Properties().Any(p => p.Name.IndexOf("Key", System.StringComparison.OrdinalIgnoreCase) >= 0))
.First();
Old solutions
You have two options, that depends on Name type:
1 - Without IEqualityComparer, and if Name in Properties is a string. replace Contains by Equals like :
var matchEle = listOfElements
.Where(e => e.Properties().Any(p => p.Name.Equals("Key", StringComparison.OrdinalIgnoreCase)))
.First();
2 - With IEqualityComparer, and if Name in Properties is a list of string:
2.1 : Create a custom comparer, like:
public class StringIEqualityComparer : IEqualityComparer<string>
{
public bool Equals(string x, string y)
{
return x.Equals(y, StringComparison.OrdinalIgnoreCase);
}
public int GetHashCode(string obj)
{
return obj.GetHashCode();
}
}
2.2 : change little your query to :
var matchEle = listOfElements
.Where(e => e.Properties().Any(p => p.Name.Contains("Key", new StringIEqualityComparer())))
.First();
I hope this helps you.
I am just not understanding the LINQ non-query syntax for GroupBy.
I have a collection of objects that I want to group by a single property. In this case Name
{ Id="1", Name="Bob", Age="23" }
{ Id="2", Name="Sally", Age="41" }
{ Id="3", Name="Bob", Age="73" }
{ Id="4", Name="Bob", Age="34" }
I would like to end up with a collection of all the unique names
{ Name="Bob" }
{ Name="Sally" }
Based on some examples I looked at I thought this would be the way to do it
var uniqueNameCollection = Persons.GroupBy(x => x.Name).Select(y => y.Key).ToList();
But I ended up with a collection with one item. So I though maybe I was over complicating things with the projection. I tried this
var uniqueNameCollection = Persons.GroupBy(x => x.Name).ToList();
Same result. I ended up with a single item in the collection. What am I doing wrong here? I am just looking to GroupBy the Name property.
var names = Persons.Select(p => p.Name).Distinct().ToList()
If you just want names
LINQ's GroupBy doesn't work the same way that SQL's GROUP BY does.
GroupBy takes a sequence and a function to find the field to group by as parameters, and return a sequence of IGroupings that each have a Key that is the field value that was grouped by and sequence of elements in that group.
IEnumerable<IGrouping<TSource>> GroupBy<TSource, TKey>(
IEnumerable<TSource> sequence,
Func<TSource, TKey> keySelector)
{ ... }
So if you start with a list like this:
class Person
{
public string Name;
}
var people = new List<Person> {
new Person { Name = "Adam" },
new Person { Name = "Eve" }
}
Grouping by name will look like this
IEnumerable<IGrouping<Person>> groups = people.GroupBy(person => person.Name);
You could then select the key from each group like this:
IEnumerable<string> names = groups.Select(group => group.Key);
names will be distinct because if there were multiple people with the same name, they would have been in the same group and there would only be one group with that name.
For what you need, it would probably be more efficient to just select the names and then use Distinct
var names = people.Select(p => p.Name).Distinct();
var uniqueNameCollection = Persons.GroupBy(x => x.Name).Select(y => y.Key).ToList();
Appears valid to me. .net Fiddle showing proper expected outcome: https://dotnetfiddle.net/2hqOvt
Using your data I ran the following code statement
var uniqueNameCollection = people.GroupBy(x => x.Name).Select(y => y.Key).ToList();
The return results were List
Bob
Sally
With 2 items in the List
run the following statement and your count should be 2.
people.GroupBy(x => x.Name).Select(y => y.Key).ToList().Count();
Works for me, download a nugget MoreLinq
using MoreLinq
var distinctitems = list.DistinctBy( u => u.Name);
Im trying to use NEST and can´t figure out how to use it together with this class
public class Metric {
public DateTime Timestamp { get; set; }
public Dictionary<string,object> Measurement { get; set; }
}
How do i use the new fluent mapping with a class like this?
Im planning to use i like this:
var mesurements = new Dictionary<string, object>();
mesurements["visits"] = 1;
mesurements["url"] = new string[] {"/help", "/about"};
connection.Index(new Metric() {
Timestamp = DateTime.UtcNow,
Measurement = mesurements
});
Will it be possible to write a query against the dictionary? If I wanted to get all Metrics from yesterday with a mesurenemt with a key name "visits", how will that look like ?
You don't have to use mapping, you can rely on elasticsearch's schemaless nature really well in this case.
The json serializer will write that out as:
{
"timestamp" : "[datestring]",
"measurement" : {
"visits" : 1,
"url" : [ "/help", "/about"]
}
}
You can query for the existence of the "measurement.visits" field like so using NEST.
var result = client.Search<Metric>(s=>s
.From(0)
.Size(10)
.Filter(filter=>filter
.Exists("measurement.visits")
)
);
result.Documents now hold the first 10 metrics with a visits key in the Measurement dictionary.
If you do want to explicitly map possible keys in that dictionary using the new fluent mapping:
var result = client.MapFluent<Metric>(m => m
.Properties(props => props
.Object<Dictionary<string,object>>(s => s
.Name(p => p.Measurement)
.Properties(pprops => pprops
.Number(ps => ps
.Name("visits")
.Type(NumberType.#integer)
)
.String(ps => ps
.Name("url")
.Index(FieldIndexOption.not_analyzed))
)
)
)
)
);
Remember that we haven't turned off dynamic mapping using this mapping so you can still inserts other keys into your dictionary without upsetting elasticsearch. Only now elasticsearch will know visits is an actual integer andwe dont want to analyze the url values.
since we are not using any typed accessors (The .Name() call is typed to Metric) .Object<Dictionary<string,object>> could be .Object<object> too.
This has been ruining my life for a few days now, time to ask...
I am using Entity Framework 4.0 for my app.
A Location (such as a house or office) has one or more facilities (like a bathroom, bedroom, snooker table etc..)
I want to display a checkbox list on the location page, with a checkbox list of facilities, with the ones checked that the location currently has.
My View Model for the facilities goes like this...
public class FacilityViewItem
{
public int Id { get; set; }
public string Name { get; set; }
public bool Checked { get; set; }
}
So when im passing the Location View Model to the UI, i want to pass a List<T> of facilities where T is of type FacilityViewItem.
To get the facilities that the location already has is simple - i make a query using Location.Facilities which returns an EntityCollection where T is of type Facility. This is because Facilities is a navigation property....
var facs = from f in location.Facilities
select new FacilityViewItem()
{
Id = f.FacilityId,
Name = f.Name,
Checked = true
};
So here is where my problem lies - i want the rest of the facilities, the ones that the Location does not have.
I have tried using Except() and Any() and Contains() but i get the same error.
Examples of queries that do not work...
var restOfFacilities = from f in ctx.Facilities
where !hasFacilities.Contains(f)
select new FacilityViewItem()
{
Id = f.FacilityId,
Name = f.Name
};
var restOfFacilities = ctx.Facilities.Except(facilitiesThatLocationHas);
var notFacs = from e in ctx.Facilities
where !hasFacilities.Any(m => m.FacilityId == e.FacilityId)
select new FacilityViewItem()
{
Id = e.FacilityId,
Name = e.Name
};
And the error i get with every implementation...
System.NotSupportedException was unhandled
Message=Unable to create a constant value of type 'Chapter2ConsoleApp.Facility'. Only primitive types ('such as Int32, String, and Guid') are supported in this context.
What am i overlooking here?
ironically enough i solved it in a matter of hours after i posted the question on here, after days of suffering.
The error is basically saying 'i dont know how to calculate what items are not included by comparing strongly typed objects. Give me a list of Ints or some simple types, and i can take care of it'.
So, first you need to get a list of the primary keys, then use that in the contains clause...
//get the primary key ids...
var hasFacilityIds = from f in hasFacilities
select f.FacilityId;
//now use them in the contains clause...
var restOfFacilities = from f in ctx.Facilities
where !hasFacilityIds.Contains(f.FacilityId)
select new FacilityViewItem()
{
Id = f.FacilityId,
Name = f.Name
};
The first query seems fine, but you need to compare the Ids:
var restOfFacilities = from f in ctx.Facilities
where !facs.Select(fac => fac.Id).Contains(f.Id)
select f;
I wanna see what's hasFacilities, anyway, as L2E shows, "Only primitive types ('such as Int32, String, and Guid') are supported in this context", so I suppose you must retrieve first the data and put into a collection of FacilityViewItem.
var restOfFacilities = ctx
.Facilities
.Where(f => !hasFacilities.Contains(f))
.Select(f => new { f.FacilityId, f.Name })
.ToList()
.Select(f => new FacilityViewItem {
Id = f.FacilityId,
Name = f.Name
});
var notFacs = ctx
.Facilities
.Where(e => !hasFacilities.Any(m => m.FacilityId == e.FacilityId))
.Select(e => new { e.FacilityId, e.Name })
.ToList()
.Select(e => new FacilityViewItem {
Id = e.FacilityId,
Name = e.Name
});
hope it helps
I am using Linq.Dynamic. I have already added another SelectMany extension to all for creating a new anonymous object with the data. But, I have ran into another issue that I can not seem to solve.
I want to have extension method chaining as follows, but using the dynamic methods:
var customerandorderflat = db.Customers
.SelectMany(c => c.Orders.SelectMany(o => o.Order_Details,
(ord, orddetail) => new
{
OrderID = ord.OrderID,
UnitPrice = orddetail.UnitPrice
}).DefaultIfEmpty(),
(cus, ord) => new
{
CustomerId = cus.CustomerID,
CompanyName = cus.CompanyName,
OrderId = ord.OrderID == null ? -1 : ord.OrderID,
UnitPrice = ord.UnitPrice
});
Ideally I would like to chain the dynamic SelectMany as follows:
db.Customers.SelectMany(c => c.Orders.SelectMany("Order_Details", "new(outer.OrderID, inner.UnitPrice)"), "new(outer.CustomerID, inner.OrderID)");
Or something to that affect. The problem is that I can not get a signature to match.
I have tried many different options to get it to allow chaining. But it just doesn't work. I am thinking ideally it would look like this:
public static IQueryable SelectMany(this IQueryable source, IQueryable innerExpression, string resultsSelector, params object[] values)
But, it doesn't recognize c => c.Orders as IQueriable. I also need to figure out how to do DefaultIfEmpty on the results to allow for LEFT JOINs.
Please help.
c.Orders is an EntitySet. EntitySet doesn't implement IQueryable. Try c.Orders.AsQueryable()
It was getting the wrong definition. Actual error when on right definition: Cannot convert lambda expression to type 'System.Linq.IQueryable' because it is not a delegate type