How to create select/deselect all checkbox?

[fred williams]

Hello,

I'm trying to add an item to the top of my treeview with a value of "Select/Deselect All" that will check all items. I have a treeview named "tvDirectory" 

I added it like this:

tvDirectory.Items.Add("Select/Deselect All");

 

Then I tried to implement the functionality in the Checked eventhandler like this:

RadTreeViewItem item = (RadTreeViewItem)((RadTreeView)sender).SelectedContainer;
if (item != null)
{

    if (item.CheckState == ToggleState.On)
    {
        foreach (RadTreeViewItem tvItem in tvDirectory.Items)
        {
            tvItem.CheckState = ToggleState.On;
        }
    }
    else
    {
        foreach (RadTreeViewItem tvItem in tvDirectory.Items)
        {
            tvItem.CheckState = ToggleState.Off;
        }
    }
}

But I get an "object reference not set to instance of an object for  "item". Help please, thanks.

[Kiril Stanoev]

Hello Fred,

I wasn't able to reproduce the issue you describe. Please take a look at my test project and let me know if I am missing something. I'd be glad to further assist you.

Best wishes,
Kiril Stanoev
the Telerik team

[fred williams]

Hello and thanks for the reply.

I've added your check and uncheck event handlers to my code, but when I run it I get an error :

"Unable to cast item of type System.String to type Telerik.Windows.Controls.RadTreeViewItem"

[fred williams]

Hello again,

I was able to get your code working. The problem I had was that I was declaring th eother items in the treeview with text values:

RadTreeViewItem item = new RadTreeViewItem("value here");

Instead of this way:

RadTreeViewItem root = new RadTreeViewItem() { Header = "Select/Deselect All" };

and that's why I was getting the string error. Thanks for all of your help.