How to disable the controls(Combo bx,Text Bx) on selection of List box values in wpf

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Dear All,

In my WPF Application, I have few controls viz., List Box(A) and ComboBox(B) and TextBox(C), I need to disable the entities, ie., If User selects (A) any value from List Box, Both items in ComboBox and TextBox should be disabled and vice versa.

For Instance,using SelectionChanged property for Listbox, intended to disable two other controls(viz., ComboBx, TextBx) using the below code behind. and xaml code

//MyFile.xaml

HTML

<ListBox Name="MyListBox"  SelectionChanged="ListBx_SelectionChanged"  ...>
.....

//MyFile.xaml.cs

C#

private void ListBx_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    MyTextbx.IsEnabled = false;
    MyComboBx.IsEnabled = false;
}

I get assertion on above change, Please let me know we can resolve the same? or any other alternative approach to target the above problem. The Exception of type "System.NullReferenceException" occurred, and was not handled in user code. Additional Information: Object Reference not set to an Instance of an Object.

Any Help in resolving the above would be appreciable.

Posted 25-Mar-12 22:06pm

Member 7985084

Updated 25-Mar-12 23:45pm

v3

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Roman Lerman · Answer 1 · 2012-03-26T01:18:00

Probably MyTextbx and MyComboBx not been yet initialized when the ListBx_SelectionChanged is handled.
Try to check MyTextbx and MyComboBx for null

private void ListBx_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
  if(MyTextbx!=null && MyComboBx!=null)
   {
    MyTextbx.IsEnabled = false;
    MyComboBx.IsEnabled = false;
   }
}