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POProblem with MessageBox.Show in catch
 

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  1. POProblem with MessageBox.Show in catch
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    <p>When I try to run the following code It causes an Unhandled Exception. After much tweeking with the code I found if commented out the MessageBox.Show line the problem goes away! Unusually I have used MessageBox.Show statments in other catch{ } segments in other parts of the code with no problems. My question is does anyone know why its causing the exception?</p> <p>(P.s Reports_Group_Chooser is a ComboBox)</p> <p>The Code:</p> <pre><code>string GroupName= (string)Reports_Group_Chooser.SelectedItem; byte[] ConfigBytes= new byte[]{}; try{ ConfigBytes= File.ReadAllBytes("Reports/"+ GroupName.ToLower() +".grp"); }catch{ MessageBox.Show("The file for this group is missing. Cannot continue.","File Error",MessageBoxButtons.OK, MessageBoxIcon.Exclamation); Reports_Group_Chooser.Items.RemoveAt(NewGroup); Reports_Group_Chooser.SelectedIndex= 0; } </code></pre> <p>The error (well most of it):</p> <blockquote> <p>Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object at System.Windows.Forms.ComboBox.DropDownListBoxFinished () [0x00000] at (wrapper remoting-invoke-with-check) System.Windows.Forms.ComboBox:DropDownListBoxFinished () at System.Windows.Forms.ComboBox+ComboListBox.HideWindow () [0x00000] at System.Windows.Forms.ComboBox+ComboListBox.OnMouseUp (System.Windows.Forms.MouseEventArgs e) [0x00000] at System.Windows.Forms.Control.WmLButtonUp (System.Windows.Forms.Message&amp; m) [0x00000] at System.Windows.Forms.Control.WndProc (System.Windows.Forms.Message&amp; m) [0x00000] at System.Windows.Forms.ComboBox+ComboListBox.WndProc (System.Windows.Forms.Message&amp; m) [0x00000] at System.Windows.Forms.Control+ControlWindowTarget.OnMessage (System.Windows.Forms.Message&amp; m) [0x00000] at System.Windows.Forms.Control+ControlNativeWindow.WndProc (System.Windows.Forms.Message&amp; m) [0x00000] at System.Windows.Forms.NativeWindow.WndProc (IntPtr hWnd, Msg msg, IntPtr wParam, IntPtr lParam) [0x00000] at System.Windows.Forms.XplatUIX11.DispatchMessage (System.Windows.Forms.MSG&amp; msg) [0x00000] at System.Windows.Forms.XplatUI.DispatchMessage (System.Windows.Forms.MSG&amp; msg) [0x00000] at System.Windows.Forms.Application.RunLoop (Boolean Modal, System.Windows.Forms.ApplicationContext context) [0x00000]</p> </blockquote> <p>Any help appreciated Michael</p> <p>UPDATE This is an example of a working MessageBox.Show in my code which does not cause an error:</p> <pre><code>GlobalConfig= new Dictionary&lt;string, string&gt;(); byte[] ConfigBytes= new byte[]{}; try{ ConfigBytes= System.IO.File.ReadAllBytes("Config.cfg"); }catch{ MessageBox.Show("Global ettings file does not exist. Cannot continue.","File Error",MessageBoxButtons.OK, MessageBoxIcon.Exclamation); GlobalConfig.Add("StoreNumber",""); GlobalConfig.Add("Error","Y"); } </code></pre> <p>Update update:</p> <p>It seems the problem is just having the MessageBox.Show within a combobox event: The following code still presents the same error:</p> <pre><code>private void Reports_GroupChanged(object sender,EventArgs e){ MessageBox.Show("The file for this group is missing. Cannot continue.","File Error",MessageBoxButtons.OK, MessageBoxIcon.Exclamation); } </code></pre>
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    1. COYou error is with the combo box not the message box. The problem is the call stack does not contain the line numbers.. Is this in WPF? APS.NET? Windows forums?
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    2. COSorry I mreally new to C# programming what do you mean "Is this in WPF? APS.NET? Windows forums? "
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