How sort a System.Collections.Generic.List in VB.Net?

Question

I using a genric list(m_equipmentList ) which is collection of objects (Schedule_Payitem).
How can sort list according to a proerty of child object ?

Dim m_equipmentList As New List(Of Schedule_Payitem)

Need to sort m_equipmentList on basis of resourceid property of Schedule_Payitem.

Thanks for asking this. I was able to use the lambda expression from Jon Skeet in one of my projects. — tooleb
– tooleb, Commented May 28, 2009 at 20:29

Jon Skeet · Accepted Answer · 2009-01-13 12:03:36Z

59

Are you using VB9? If so, I'd use a lambda expression to create a Comparer(Of Schedule_PayItem). Otherwise, write a short class to implement IComparer(Of Schedule_PayItem). pass whichever one you've got into List.Sort.

An example for the lambda expression (untested):

m_equipmentList.Sort(Function(p1, p2) p1.ResourceID.CompareTo(p2.ResourceID))

And for the IComparer(Of Schedule_PayItem):

Public Class PayItemResourceComparer
    Implements IComparer(Of Schedule_PayItem)
    Public Function Compare(ByVal p1 As Schedule_PayItem, _
                            ByVal p2 As Schedule_PayItem) As Integer
        Return p1.ResourceID.CompareTo(p2.ResourceID)
    End Function
End Class

...

m_equipmentList.Sort(New PayItemResourceComparer)

edited Jan 13, 2009 at 12:03

answered Jan 13, 2009 at 11:55

Jon Skeet

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1 Comment

Kyle B. Over a year ago

Helpful tip to specify Collections.Generic.IComparer(Of Schedule_PayItem). I was getting an error: 'System.Collections.IComparer' has no type parameters. A little searching helped me find that two such interfaces with same name exist, one in System.Collections and another in System.Collections.Generic.

Pablo Retyk · Accepted Answer · 2009-01-13 12:03:01Z

7

I don't know vb.net so I did it in C#

m_equipmentList.Sort(
   (payItem1,payItem2)=>payItem1.ResourceID.CompareTo(payItem2.ResourceID));

and using the reflector translated it to vb.net hope it helps

m_equipmentList.Sort(
Function (ByVal payItem1 As Schedule_Payitem, ByVal payItem2 As Schedule_Payitem) 
    Return payItem1.ResourceID.CompareTo(payItem2.ResourceID)
End Function)

or you can inherit Schedule_Payitem from IComparable and implement CompareTo and then just call m_equipmentList.Sort()

edited Jan 13, 2009 at 12:03

answered Jan 13, 2009 at 11:54

Pablo Retyk

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1 Comment

CodingBarfield Over a year ago

This is a great way for lots of problems :D

dandan78 · Accepted Answer · 2011-04-12 18:37:30Z

5

You can accomplish sorting the list in descending order by changing this-

m_equipmentList.Sort(
Function (ByVal payItem1 As Schedule_Payitem, ByVal payItem2 As Schedule_Payitem) 
    Return payItem1.ResourceID.CompareTo(payItem2.ResourceID)
End Function)

to this

m_equipmentList.Sort(
Function (ByVal payItem1 As Schedule_Payitem, ByVal payItem2 As Schedule_Payitem) 
    Return payItem2.ResourceID.CompareTo(payItem1.ResourceID)
End Function)

edited Apr 12, 2011 at 18:37

dandan78

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answered Apr 11, 2011 at 18:39

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Comments

cmsjr · Accepted Answer · 2009-01-13 11:55:14Z

0

Try this

Dim m_equipmentList As New List(Of Schedule_Payitem)


m_equipmentList.Sort(delegate(Schedule_Payitem p1, Schedule_Payitem p2)
              {
                  return p1.resourceid .CompareTo(p2.resourceid );
              });

edited Jan 13, 2009 at 11:55

answered Jan 13, 2009 at 11:48

cmsjr

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2 Comments

Joel Coehoorn Over a year ago

VB.Net doesn't have anonymous delegate support until vs2008, so the conversion from this code may not be trivial.

schlebe Over a year ago

You code is a mix of C# and VB.Net ! ';' character at end of line is for C# !

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