Issue with ListView Control

elaverick · 04-28-2008, 02:53 PM

This is driving me crazy. I have a listview control on form in VC# 2008 Express.
There are three colums set in its properties and its in details mode. I'm trying to add rows of data in at run time but any time I try and access the list Items (either to Add or Clear) I'm told that I have a NullReferenceException and that "Object reference not set to an instance of an object."

What am I doing wrong?

Code:

ListViewItem item = new ListViewItem("NewItem");
item.SubItems.AddRange( new string[] { "SubItem1", "SubItem2" });

lvProcesses.Items.Add("item");

indigo0086 · 04-28-2008, 04:02 PM

It's easier to have a data binding source associated with the list view, then set the data source to a bindingList that contains your element type, and the DataMember property set to the data the BindingList Holds. Then when you add your stuff to the bindinglist, it automatically updates the listview control.

elaverick · 04-29-2008, 12:06 AM

Unfortunatly that's not really an option here, I'm trying to populate the ListView with the list of processes currently running on a target system. So it has to be done at runtime.

vart · 04-29-2008, 12:11 AM

What is lvProcesses?

elaverick · 04-29-2008, 12:12 AM

lvProcesses is just the ListView Control itself

vart · 04-29-2008, 12:23 AM

it seems to me you are trying to add string "item" instead of object ListViewItem item

elaverick · 04-29-2008, 12:26 AM

I've had it both ways around, neither works. The string version is a valid version of the overloaded method, but the issue seems to be that the ListViewItemContainter Items (that's lvProcesses.Itemsin this case) hasn't been instanciated, however you can't individually instaciate it as its read only.

Magos · 04-29-2008, 01:20 AM

1) You forgot to (manually) create a System.Windows.Forms.ListView object and assign it to lvProcesses
2) You are trying to add the item before the call to InitializeComponent (in your form class)

1) is if you create your controls manually, 2) is if you're using the visual designer

elaverick · 04-29-2008, 03:42 AM

Quote:

Originally Posted by Magos

1) You forgot to (manually) create a System.Windows.Forms.ListView object and assign it to lvProcesses
2) You are trying to add the item before the call to InitializeComponent (in your form class)

1) is if you create your controls manually, 2) is if you're using the visual designer

Ahaha!! Fantastic thanks, I'd put it in the Initial method of the form to test things but before InitalizeComponents had been called as a test. That's solved it

04-28-2008, 02:53 PM	#1
elaverick Registered User Join Date: Apr 2008 Posts: 5	Issue with ListView Control This is driving me crazy. I have a listview control on form in VC# 2008 Express. There are three colums set in its properties and its in details mode. I'm trying to add rows of data in at run time but any time I try and access the list Items (either to Add or Clear) I'm told that I have a NullReferenceException and that "Object reference not set to an instance of an object." What am I doing wrong? Code: ListViewItem item = new ListViewItem("NewItem"); item.SubItems.AddRange( new string[] { "SubItem1", "SubItem2" }); lvProcesses.Items.Add("item");
elaverick is offline

04-28-2008, 04:02 PM	#2
indigo0086 Ethernal Noob Join Date: Nov 2001 Posts: 1,891	It's easier to have a data binding source associated with the list view, then set the data source to a bindingList that contains your element type, and the DataMember property set to the data the BindingList Holds. Then when you add your stuff to the bindinglist, it automatically updates the listview control.
indigo0086 is offline

04-29-2008, 12:06 AM	#3
elaverick Registered User Join Date: Apr 2008 Posts: 5	Unfortunatly that's not really an option here, I'm trying to populate the ListView with the list of processes currently running on a target system. So it has to be done at runtime.
elaverick is offline

04-29-2008, 12:11 AM	#4
vart CSharpener Join Date: Oct 2006 Posts: 5,336	What is lvProcesses? __________________ If I have eight hours for cutting wood, I spend six sharpening my axe.
vart is offline

04-29-2008, 12:12 AM	#5
elaverick Registered User Join Date: Apr 2008 Posts: 5	lvProcesses is just the ListView Control itself
elaverick is offline

04-29-2008, 12:23 AM	#6
vart CSharpener Join Date: Oct 2006 Posts: 5,336	it seems to me you are trying to add string "item" instead of object ListViewItem item __________________ If I have eight hours for cutting wood, I spend six sharpening my axe.
vart is offline

04-29-2008, 12:26 AM	#7
elaverick Registered User Join Date: Apr 2008 Posts: 5	I've had it both ways around, neither works. The string version is a valid version of the overloaded method, but the issue seems to be that the ListViewItemContainter Items (that's lvProcesses.Itemsin this case) hasn't been instanciated, however you can't individually instaciate it as its read only.
elaverick is offline

04-29-2008, 01:20 AM	#8
Magos Confused Join Date: Sep 2001 Location: Sweden Posts: 3,125	1) You forgot to (manually) create a System.Windows.Forms.ListView object and assign it to lvProcesses 2) You are trying to add the item before the call to InitializeComponent (in your form class) 1) is if you create your controls manually, 2) is if you're using the visual designer __________________ MagosX.com Give a man a fish and you feed him for a day. Teach a man to fish and you feed him for a lifetime.
Magos is offline

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