AutoCompleteBox: NullReferenceException in PopulateComplete

03-30-2009 6:46 AM |

If LostFocus sets binding property to null
NullReferenceException occurs in PopulateComplete.
How to fix ?

Andrus.

<toolkit:AutoCompleteBox
Text="{Binding Value,Mode=TwoWay}"
LostFocus="AutoCompleteBox_LostFocus"
Populating="AutoCompleteBox_Populating"
Tag="{Binding}"
/>

class FormField {
  public string Value;
}

void AutoCompleteBox_LostFocus(object sender, RoutedEventArgs e)
{
            AutoCompleteBox ac = (AutoCompleteBox)sender;
            var formField = (FormField)ac.Tag;
            formField.Value = null;
}

void AutoCompleteBox_Populating(object sender, PopulatingEventArgs e) {
var box=(AutoCompleteBox)sender;
proxy.GetPickListCompleted += (s, args) => {
   box.ItemsSource = args.Result;
  // NRE occurs here:
  box.PopulateComplete();
};
}

System.NullReferenceException was unhandled by user code
  Message="Object reference not set to an instance of an object."
  StackTrace:
       at System.Windows.Controls.AutoCompleteBox.UpdateTextCompletion(Boolean userInitiated)
       at System.Windows.Controls.AutoCompleteBox.PopulateComplete()
       at AutoForm.PageViewModel.<>c__DisplayClass5.<Populate>b__4(Object s, GetPickListCompletedEventArgs args)
       at AWSilverlightLOB.StockServiceReference.StockServiceSoapClient.OnGetPickListCompleted(Object state)

Re: AutoCompleteBox: NullReferenceException in PopulateComplete

03-31-2009 8:23 PM |

Hi,

This is related to your custom web client and/or WCF service. Can you provide more details?

Re: AutoCompleteBox: NullReferenceException in PopulateComplete

04-01-2009 10:29 AM |

How to provide details ?

This forum does not allow to attach files to messages.

Re: AutoCompleteBox: NullReferenceException in PopulateComplete

04-01-2009 12:07 PM |

Binding to the Text property may not be the best way to go here, since that could set Text to null. How about using the ValueMemberBinding and/or SelectedItem properties instead?

Re: AutoCompleteBox: NullReferenceException in PopulateComplete

04-02-2009 1:05 PM |

I replaced 

Text="{Binding Value,Mode=TwoWay}"

 with