none
how to handle NullReferenceException

    Question

  •  Hi i'm trying to execute the fallowing code but it shows NullRefereneException can anybody know the solution for this

    this is my xaml.cs file

    using System;
    using System.IO;
    using System.Net;
    using System.Windows;
    using System.Windows.Controls;
    using System.Windows.Data;
    using System.Windows.Media;
    using System.Windows.Media.Animation;
    using System.Windows.Navigation;

    namespace Test
    {
     public partial class Scene1
     {
      
      public Scene1()
      {
      }


      private void image(object sender, System.Windows.RoutedEventArgs e)
      {
       RichTextEditor.AppendText ("Stroke method executed");
      }

      private void selectShape(object sender,  System.Windows.Controls.SelectionChangedEventArgs e)
      {
                RichTextEditor.AppendText ("Combobox method executed");
             }

     }
    }

     

    and this is my .xaml file

    <Grid
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
     xmlns:d="http://schemas.microsoft.com/expression/interactivedesigner/2006"
     mc:Ignorable="d"
     Background="#FFFFFFFF"
     x:Name="DocumentRoot"
     x:Class="Test.Scene1"
     Width="640" Height="480">

     <Grid.Resources>
      <Storyboard x:Key="OnLoaded"/>
     </Grid.Resources>

     <Grid.Triggers>
      <EventTrigger RoutedEvent="FrameworkElement.Loaded">
       <BeginStoryboard x:Name="OnLoaded_BeginStoryboard" Storyboard="{DynamicResource OnLoaded}"/>
      </EventTrigger>
     </Grid.Triggers>
     
     <Grid.ColumnDefinitions>
      <ColumnDefinition/>
     </Grid.ColumnDefinitions>
     <Grid.RowDefinitions>
      <RowDefinition/>
     </Grid.RowDefinitions>
     
     
     <Canvas HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Margin="1.00000000000011,-0.999999999999915,0,-2.00000000000006" Width="Auto" Height="Auto" x:Name="Canvas" RenderTransformOrigin="0.5,0.5" Grid.ColumnSpan="1" OpacityMask="sc#1, 0.244989648, 0.213771492, 0.8823977">
      <TabControl Width="630" Height="88" Canvas.Left="2.00000000000032" Canvas.Top="0" x:Name="TabControl" TabStripPlacement="Top">
       <TabItem x:Name="Insert" Header="Insert">
        <WrapPanel>
         <Button HorizontalAlignment="Left" VerticalAlignment="Top" Width="70" Height="25" Content="Text" VerticalContentAlignment="Center"/>
        </WrapPanel>
       </TabItem>
       <TabItem x:Name="Edit" Header="Edit">
        <WrapPanel>
         <Button HorizontalAlignment="Left" VerticalAlignment="Top" Width="70" Height="25" VerticalContentAlignment="Center" Content="Cut"/>
         <Button HorizontalAlignment="Left" VerticalAlignment="Top" Width="70" Height="25" Content="Copy" VerticalContentAlignment="Center" />
         <Button HorizontalAlignment="Left" VerticalAlignment="Top" Width="70" Height="25" Content="Paste" VerticalContentAlignment="Center"/>
        </WrapPanel>
       </TabItem>
       <TabItem x:Name="Drawing" Header="Drawing">
        <WrapPanel>
         <Label Content ="Shape :"/>
         <ComboBox x:Name ="shapes" Height ="25" Width ="100" SelectionChanged="selectShape">
          <ComboBoxItem Content="Line"/>
          <ComboBoxItem IsSelected ="True" Content="Circle"/>
          <ComboBoxItem Content="Rectangle"/>
          <ComboBoxItem Content="Ovel"/>
         </ComboBox>
         <Button HorizontalAlignment="Left" VerticalAlignment="Top" Width="70" Height="25" Content="Stroke" VerticalContentAlignment="Center" Click="image"/>
         
        </WrapPanel>
       </TabItem>
      </TabControl>
     </Canvas>
              
      <RichTextBox Grid.Column="0" Grid.Row="0" x:Name="RichTextEditor" AcceptsReturn="True" Background="sc#1, 0.941325068, 0.940964162, 0.940411448" d:LayoutOverrides="VerticalAlignment" Margin="3.00000000000773,89.9420289855063,0,0" Grid.ColumnSpan="1" VerticalAlignment="Top" Height="358.513513513508" HorizontalAlignment="Left" Width="630" Canvas.Left="2" Canvas.Top="35.9999999999998" RenderTransformOrigin="0,0" ToolTip="U Can Drag and drop here" AcceptsTab="True" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">
      <RichTextBox.RenderTransform>
       <TransformGroup>
        <TranslateTransform X="0" Y="0"/>
        <ScaleTransform ScaleX="1" ScaleY="1.0724637681159421"/>
        <SkewTransform AngleX="0" AngleY="0"/>
        <RotateTransform Angle="0"/>
        <TranslateTransform X="0" Y="0"/>
        <TranslateTransform X="0" Y="0"/>
       </TransformGroup>
      </RichTextBox.RenderTransform>
              <FlowDocument AllowDrop="True" FontSize="11" FontFamily="TimesNewRoman" TextAlignment="Left">
        <Paragraph/>
        
       </FlowDocument>
            </RichTextBox>
    </Grid>

     

    thanx - Sai

    Monday, May 08, 2006 7:36 PM

Answers

  • Ya i got solution i just remove the default selection of combobox item then its for fine

    thanx - Sai

     

    Tuesday, May 09, 2006 7:45 AM

All replies

  • To help you out, we would need details for the NullRefException(stack trace, ...) as well as any inner exception details...
    Monday, May 08, 2006 8:45 PM
  • hi,

    this is the inner details of the exception:

    "Object Reference not set to an instance of an object"

    and i get this exception when i use it for ComboBox,

    when i use the same for Button it is not raising the exception.

    why is it so?

    thanx,

    Sai

    Tuesday, May 09, 2006 5:13 AM
  • Give a try to this:

    private void selectShape(object sender,  RoutedEventArgs e)
      {
                RichTextEditor.AppendText ("Combobox method executed");
       }

    Tuesday, May 09, 2006 7:23 AM
  • Ya i got solution i just remove the default selection of combobox item then its for fine

    thanx - Sai

     

    Tuesday, May 09, 2006 7:45 AM