Passing a type and list(of Objects) to a function for it to later cast the object to a specific type

Question

0.00/5 (No votes)

See more:

I don't see a way of making this easier/shorter, right now i have the following

VB

Sub DisplayObjects(ByRef Form As Form, ByRef listBox As ListBox, ByVal FinalIndexOfListBox As Integer)


       Select Case (Form.Name)

           Case (FrmConfigureDepartments.Name) 'Departments
               EnableEvents = False 'we dont want the listbox index changed event to fire so we disable the events until we are done
               listBox.Items.Clear()

               For Each Obj In ModuleTimeClock.DAL.GetDepartments
                   listBox.Items.Add(Obj)
               Next
               EnableEvents = True 'enable events again so when we set the index to 0 it displays the objects properties
               listBox.SelectedIndex = FinalIndexOfListBox

               Case()

       End Select

   End Sub

I would like to be able to declare the function as

Sub DisplayObjects(ByRef Form As Form, ByRef listBox As ListBox, ByVal FinalIndexOfListBox As Integer,ObjectType as Type,ObjectList as List(of Objects))

And then just say

VB

For Each Obj In ObjectList
                  listBox.Items.Add(Ctype(Obj,ObjectType))
              Next

But i can;t seem to find a way of doing this, i would prefer this way cause if i have to do the previous, then i would have to repeat that code 13 more times, due to apssing in Depeartment,Users,Activities,Shifts Etc..
Any help on this would be greatly appreciated THANKS in Advance :)

Posted 15-Aug-14 15:20pm

displayaname

Add a Solution

Comments

Dave Kreskowiak 15-Aug-14 22:36pm

What is this for? If it is what I think it's for, it's a pretty bad idea.

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Dave Kreskowiak · Accepted Answer · 2014-08-16T05:05:00

OK, that's what I thought. Bad idea.

Look at what you're doing in your Select Case. This is writing code specific to each form. That kind of code belongs on the form it's responsible for, not in some code that aspires to be the "Be-All End-All" to populating controls on a form.

A better way to do this would be an extension method for IEnumberable(Of T). Now you're not passing any type information about the list you're sending. All you need to specify is the ListBox your populating:

Imports System.Collections.Generic
Imports System.Runtime.CompilerServices

Module Extensions

    <extension()>
    Public Sub SendToListBox(Of T)(list As IEnumerable(Of T), target As ListBox)
        If target Is Nothing Then
            Throw New ArgumentNullException("target")
        End If

        target.BeginUpdate()
        target.Items.Clear()

        For Each item In list
            target.Items.Add(item)
        Next

        target.EndUpdate()
    End Sub

End Module

Though, in your example, I have no idea what EnableEvents is so that can't be incorporated into the extension.

Now all you have to do to populate a ListBox is:

myCollection.SendToListBox(someListBox)