Combine two list(of T) collections to contain distict objects

Question

User1909155429 posted

Hi,

I have the following list collection that i want to combine with another List(of Items) collection

Dim ilistValues As IList(Of Product)

The List(of items) should first be filtered to contain only objects that have a property Name="First"

then joined with ilistValues collection and filtered to contain Product with DISTICT 'Email' property.

Answer 1

User197322208 posted

var q = iListValues.Where(item=>item.Name=="First").ToList()

See also the Distinct function

then use addrange.

Answer 2

User1909155429 posted

Is that related to a Custom object ?

Because it does not work with my ILIST(OF PRODUCT)

Also, is it possible to join two List  collections together through a Query and amalgamate into one ?

Thanks

Answer 3

User281315223 posted

If you have two seperate collections (of the same kind of items), you can use the AddRange() method available through LINQ to merge two collections into one. In your case, you could also use LINQ to apply the necessary filtering (through the Distinct() method or otherwise) and then merge your collections : 

'Your first collection (you can also apply filters here through a Where clause)'
Dim a = YourCollectionOfItems.Distinct().ToList()

'Your second collection'
Dim b = YourOtherCollectionOfItems.Distinct().ToList()

'Your merged collection
Dim c = a.AddRange(b)

So your case might look something like this : 

'Your first collection (you can also apply filters here through a Where clause)'
Dim firstNames = YourFirstCollection.Where(Function (f) f.FirstName = "First").ToList() 

However to use a distinct on a specific property, you might want to consider using a third-party library like MoreLINQ which has a DistinctBy() method that may prove useful in a situation like this and it would allow you to get all of the objects with distinct email address values by using the following syntax : 

Dim emailAddresses = YourCollection.DistinctBy(Function(f) f.Email).ToList()

so you would combine both of these into : 

Dim firstNames = YourCollection.Where(Function (f) f.FirstName = "First").ToList() 
Dim emailAddresses = YourCollection.DistinctBy(Function (f) f.Email).ToList()

'Build your final collection by storing both results in a single collection'
Dim collection = firstNames.AddRange(emailAddresses)

If you wanted to perform an actual JOIN, you would likely want to the available Join() method through LINQ.

Answer 4

User-1016547394 posted

Imports System
Imports System.Collections.Generic
Class Example
    Public Shared Sub Main()
        Try 

            Dim boxEqC As New BoxEqualityComparer()

            Dim boxes As Dictionary(Of Box, [String]) = _
                        New Dictionary(Of Box, String)(boxEqC)

            Dim redBox As New Box(4, 3, 4)
            Dim blueBox As New Box(4, 3, 4)

            boxes.Add(redBox, "red")
            boxes.Add(blueBox, "blue")

        Catch argEx As ArgumentException
            Console.WriteLine(argEx.Message)
        End Try 
    End Sub 
End Class 

Public Class Box
    Public Sub New(ByVal h As Integer, ByVal l As Integer, _
                                        ByVal w As Integer)
        Me.Height = h
        Me.Length = l
        Me.Width = w
    End Sub 
    Private _Height As Integer 
    Public Property Height() As Integer 
        Get 
            Return _Height
        End Get 
        Set(ByVal value As Integer)
            _Height = value
        End Set 
    End Property 
    Private _Length As Integer 
    Public Property Length() As Integer 
        Get 
            Return _Length
        End Get 
        Set(ByVal value As Integer)
            _Length = value
        End Set 
    End Property 
    Private _Width As Integer 
    Public Property Width() As Integer 
        Get 
            Return _Width
        End Get 
        Set(ByVal value As Integer)
            _Width = value
        End Set 
    End Property 
End Class 


Class BoxEqualityComparer
    Implements IEqualityComparer(Of Box)

    Public Overloads Function Equals(ByVal b1 As Box, ByVal b2 As Box) _
                   As Boolean Implements IEqualityComparer(Of Box).Equals

        If b1.Height = b2.Height And b1.Length = _
                b2.Length And b1.Width = b2.Width Then 
            Return True 
        Else 
            Return False 
        End If 
    End Function 


    Public Overloads Function GetHashCode(ByVal bx As Box) _
                As Integer Implements IEqualityComparer(Of Box).GetHashCode
        Dim hCode As Integer = bx.Height Xor bx.Length Xor bx.Width
        Return hCode.GetHashCode()
    End Function 

End Class

Answer 5

User1909155429 posted

   pr = From p In product.Values Group p.Price By Key = p.Email Into Group = Group _
                  Select New With {.Email = Key, .Price = Group.Sum()}

i have been working with a linq query like this.

i have another custom list collection  list(of product)

i want to find the product that match on email property without   enumerating pr ?

 i use linq here because it is convenient for sum the Price into groups (Email)

  

 

Answer 6

User1909155429 posted

is this the method used for comparing custom type objects ?

and not those given previous ?

Thanks