Runtime Exception while trying to close dynamically created MetroTabItem

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C#

WPF

Hi,
I am using MahApps.Metro controls in my wpf app.
I am adding MetroTabItem to MetroTab control on button click.
> getting exception while trying to close MetroTabItem .

Exception Msg: Operation is not valid due to the current state of the object.

using the following code to add TabItem at runtime.

MetroTabItem tbItem = new MetroTabItem();
tbItem.Header = "RunTime";
tbItem.CloseButtonEnabled = true;
TextExamples cnt = new TextExamples();
tbItem.Content = cnt;
MainTabctrl.Items.Add(tbItem);

The MetroTabItems created on public Window() (i.e form loading), not showing any problem with the same code given above.

please help me to solve the issue.
Thanks in advance..