Adding a parameter to a FindAll for a Generic List in VB.NET?

Create a wrapper class that inherits from whatever Generic List you want. Then, overload the FindAll method Edit Added operator Enum to give it a little more flexibility. You should be able to extend from there Module Module1 Sub Main() Dim source As New IntList source.

Add(1) source. Add(2) source. Add(3) source.

Add(4) Dim newList As List(Of Integer) = source. FindAll(IntList.Operators. GreaterThan, 2) For Each I As Integer In newList Console.

WriteLine(i. ToString) Next Console. WriteLine("Press any key..............") Console.ReadLine() End Sub End Module Public Class IntList Inherits Generic.

List(Of Integer) Enum Operators Equal NotEqual GreaterThan GreaterThanEqualTo LessThan LessThanEqualTo End Enum Private _Val As Integer = Nothing Private _Op As Operators = Nothing Public Overloads Function FindAll(ByVal Operator As Operators, ByVal Val As Integer) As List(Of Integer) _Op = Operator _Val = Val Return MyBase. FindAll(AddressOf MyFunc) End Function Function MyFunc(ByVal item As Integer) As Boolean Select Case _Op Case Operators. Equal Return item = _Val Case Operators.

NotEqual Return item _Val Case Operators. GreaterThan Return item > _Val Case Operators. GreaterThanEqualTo Return item >= _Val Case Operators.

LessThan Return item.

Create a wrapper class that inherits from whatever Generic List you want. Then, overload the FindAll method. Edit Added operator Enum to give it a little more flexibility.

You should be able to extend from there. Module Module1 Sub Main() Dim source As New IntList source. Add(1) source.

Add(2) source. Add(3) source. Add(4) Dim newList As List(Of Integer) = source.

FindAll(IntList.Operators. GreaterThan, 2) For Each I As Integer In newList Console. WriteLine(i.

ToString) Next Console. WriteLine("Press any key..............") Console.ReadLine() End Sub End Module Public Class IntList Inherits Generic. List(Of Integer) Enum Operators Equal NotEqual GreaterThan GreaterThanEqualTo LessThan LessThanEqualTo End Enum Private _Val As Integer = Nothing Private _Op As Operators = Nothing Public Overloads Function FindAll(ByVal Operator As Operators, ByVal Val As Integer) As List(Of Integer) _Op = Operator _Val = Val Return MyBase.

FindAll(AddressOf MyFunc) End Function Function MyFunc(ByVal item As Integer) As Boolean Select Case _Op Case Operators. Equal Return item = _Val Case Operators. NotEqual Return item _Val Case Operators.

GreaterThan Return item > _Val Case Operators. GreaterThanEqualTo Return item >= _Val Case Operators. LessThan Return item LessThanEqualTo Return item.

A more generic solution is make a generic helper class, and initialize them with the reference value. Because, if you need a integer list, and in another hand a double list, you must implement two classes, but, with this approach you use only one. Module Question1747687 Class OperatorHelper(Of refType) Public ReferenceValue As refType Sub New(ByVal value As refType) ReferenceValue = value End Sub Public Function Equal(ByVal comp As refType) As Boolean Return ReferenceValue.

Equals(comp) End Function Public Function NotEqual(ByVal comp As refType) As Boolean Return Not ReferenceValue. Equals(comp) End Function Public Function GreaterThan(ByVal comp As refType) As Boolean Return Compare(comp, ReferenceValue) > 0 End Function Public Function GreaterThanEqualTo(ByVal comp As refType) As Boolean Return Compare(comp, ReferenceValue) >= 0 End Function Public Function LessThan(ByVal comp As refType) As Boolean Return Compare(comp, ReferenceValue) Add(1) source. Add(2) source.

Add(3) source. Add(4) helper = New OperatorHelper(Of Integer)(2) Dim newlist As List(Of Integer) = source. FindAll(AddressOf helper.

LessThanEqualTo) For Each I As Integer In newlist Console. WriteLine(i. ToString) Next Console.ReadLine() End Sub End Module With this code, you create the helper and you could encapsulate the comparison logic.

Based on the explanations above and from further digging around ... seems the straight answer is there's no direct VB translation. VBers have to go the long way round, at least in VS2005. In the end we used the Paul Stovell example which was the clearest solution I could find.

This is working fine for us.

I think you can do this objectList. FindAll(AddressOf MyFunc) Function MyFunc (ByVal item As testObject) Return item. _groupLevel = desiredGroupLevel End Function This is off the top of my head, so I'm not sure if it's correct.

But the idea is that you can use AddressOf to call another routine to perform actions on each item in the list. EDIT: Code example: Module Module1 Sub Main() Dim source As New List(Of Integer) source. Add(1) source.

Add(2) source. Add(3) source. Add(4) Dim newList As List(Of Integer) = source.

FindAll(AddressOf MyFunc) End Sub Function MyFunc(ByVal item As Integer) As Boolean Return item > 3 End Function End Module.

Yes, that works nicely but it's not parameterized which is really the whole point. The line "Return item > 3" ... how to parameterize the 3. – hawbsl Nov 17 '09 at 12:14 Ah, I misunderstood that requirement.In that case you will have to create a wrapper function, similar to what brad suggested.

– Jason Evans Nov 17 '09 at 13:10.

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