Summing multiple columns by one column in LINQ

Dear Experts,

I have a data table in a dataset in code. the data table has four columns customerid, month,  ActiveDays, Purchase_Amt

I want to sum  ActiveDays and  Purchase_Amt by customer (total  ActiveDays and Purchase_Amt by customer)

I am thinking of using LINQ, but i have not yet gotten how to go about it.


Anthony MatovuBusiness Analyst, MTN UgandaAsked:
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NorieAnalyst Assistant Commented:

Assuming CustomerID is numeric you could try something like this.
	Dim query = From row In dt
			Group row By CustomerID= row.Field(Of Int32)("CustomerID") Into CustomerGroup  = Group
        	Select New With {
            	Key CustomerID,
            	.TotalActivityDays = CustomerGroup.Sum(Function(r) r.Field(Of Int32)("ActiveDays")),
            	.TotalPurchaseAmt = CustomerGroup.Sum(Function(r) r.Field(Of Decimal)("Purchase_Amt"))

		For Each x In query
    		    Console.WriteLine("{0} {1} {2}", x.CustomerID, x.TotalActivityDays, x.TotalPurchaseAmt)
		Next x

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Like this:
Imports System.ComponentModel
Imports System.Runtime.CompilerServices

Module Module1
	Sub Main()
		Dim table = (From i In Enumerable.Range(1, 20) Select New With {.CustomerID = If(i Mod 5 = 0, 5, If(i Mod 4 = 0, 4, If(i Mod 3 = 0, 3, If(i Mod 2 = 0, 2, 1)))), .Month = 12 \ i, .ActiveDays = i * 9, .Purchase_Amt = i * 9 / 3}).ConvertToDataTable("Customers")
		Dim sums = (From row In table.AsEnumerable()
					Group row By CustomerID = row("CustomerID") Into g = Group
					Select New With {.CustomerID = CustomerID, .ActiveDays = g.Sum(Function(row) row("ActiveDays")), .Purchase_Amt = g.Sum(Function(row) row("Purchase_Amt"))})
		For Each sum In sums
	End Sub
End Module

Module Extensions
	Sub DrawHorizontalSeparator(ByVal width As Integer, ByVal separator As Char)
		Console.WriteLine(New String(separator, width))
	End Sub

	Public Function ConvertToDataTable(Of T)(ByVal source As IEnumerable(Of T), Optional ByVal name As String = Nothing) As DataTable
		Dim properties As PropertyDescriptorCollection = TypeDescriptor.GetProperties(GetType(T))
		Dim table As DataTable = New DataTable(If(Not String.IsNullOrWhiteSpace(name), name, String.Empty))

		For i As Integer = 0 To properties.Count - 1
			Dim [property] As PropertyDescriptor = properties(i)
			If [property].PropertyType.IsGenericType AndAlso [property].PropertyType.GetGenericTypeDefinition().Equals(GetType(Nullable)) Then
				table.Columns.Add([property].Name, [property].PropertyType.GetGenericArguments()(0))
				table.Columns.Add([property].Name, [property].PropertyType)
			End If

		Dim values(properties.Count - 1) As Object
		For Each item As T In source
			For i As Integer = 0 To properties.Count - 1
				values(i) = properties(i).GetValue(item)

		Return table
	End Function

	Public Sub PrintToConsole(ByVal table As DataTable)
		Dim width = (25 * table.Columns.Count) + table.Columns.Count
		Console.WriteLine("Table Name: {0}", table.TableName)
		Console.WriteLine("|{0}|", String.Join("|", table.Columns.Cast(Of DataColumn)().Select(Function(x) String.Format("  {0}  ", x.ColumnName).PadRight(25))))
		For Each row As DataRow In table.Rows
			Console.WriteLine("|{0}|", String.Join("|", row.ItemArray.Select(Function(x) String.Format("  {0}  ", x.ToString()).PadRight(25))))
	End Sub
End Module

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Which produces the following output -Capture.PNG-saige-

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Yeah what Norie said.  :D

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