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First off, you're getting the square because you're trying to set RTF codes using the Text property, which has no knowledge of RTF codes. (And you're not using the @ symbol in front of your string, so C# thinks "\b" is an escape character. Either make it a string literal or escape the backslash "\\b".)
If you want direct access to the RTF codes in a RichTextBox, you should use the Rtf or SelectedRtf properties.
However, I don't think that's what you're looking for, as it will make it quite a bit more difficult than using SelectionFont, SelectionColor, etc. The Rtf and SelectedRtf properties will give you the entire Rtf formatting string for the contents of the control or selection, respectively. There are intended more for pasting RTF from other sources. You can't use them to simply turn bold or color on or off.
Charlie
if(!curlies){ return; }
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Hi,
I'm populating a DataTable in a DataGrid via asynchronous callbacks. Right now my program is single-threaded and I add each "event" (actually a MSMQ msg) to a Queue using lock in the PeekCompletedHandler. I process MSMQ peeks by firing a timer every 3 seconds and, if the queue has events, dequeue the msgs with lock.
Sometimes the program will run for hours with no problems. Sometimes I get an exception saying a Generic GDI+ error has occurred and the DataGrid's screen real-estate is blanked-out and has a big red "X" throught it.
I can't figure out what it causing this. Does anybody what is wrong and how I fix this?
TIA,
Matt
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If you're setting (and even getting sometimes) properties or calling methods on controls from your asynchronous callbacks, are you using Control.Invoke? It's important that when modifying a control from another thread (which async calls are on) that you make the changes in the thread on which the control was created. See the Control.Invoke method and Control.InvokeRequired property documentation in the .NET Framework SDK for more information.
Why does it works sometimes? It's not absolute behavior to fail or succeed (well, not in all cases) if you do modify a control from a different thread than what it was created on. It basically comes down to the Windows messaging system that is used for Windows Forms and the threads that the message pumps are running on. More information can be found in the .NET Framework SDK.
Another possibility is that you're not disposing disposable objects. While you'll typically run into memory problems, other strange things can happen as well (like depleating available handles). Telling us exact what the error was may help.
Microsoft MVP, Visual C#
My Articles
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Heath,
Thanks for your reply. Re: InvokeRequired; my program does not start any threads. My PeekCompletedHandler function is appended to the end of my post. Also, when I get the "Generic GDI+ exception" I don't see any specific info about the error in the MessageBox. How do I get that info so I can post it here?
-Matt
=============================================================
private static void MQPeekCompletedHandler(Object source, PeekCompletedEventArgs peekArgs)
{
MessageQueue mq = null;
try
{
mq = (MessageQueue) source;
if(mq == null)
{
MessageBox.Show("Source was null", "MQPeekCompletedHandler()");
return;
}
if(peekArgs.AsyncResult.IsCompleted == false)
{
MessageBox.Show("IsCompleted=false", "MQPeekCompletedHandler()");
return;
}
System.Messaging.Message msg = mq.EndPeek(peekArgs.AsyncResult);
IceEvent oEvent = new IceEvent(mq, msg);
if((oEvent.IsEventValid) && (s_nvcMsgsSeen[oEvent.Identifier] == null))
{
s_nvcMsgsSeen[oEvent.Identifier] = "Y";
lock(s_MQEventQueue.SyncRoot)
{
s_MQEventQueue.Enqueue(oEvent);
}
}
}
catch(System.Messaging.MessageQueueException smmqe)
{
// The IOTimeouts occur because, as per the MS MSMQ Best Practices, we timeout our
// Asnychronous BeginPeek() methods.
if(smmqe.MessageQueueErrorCode != System.Messaging.MessageQueueErrorCode.IOTimeout)
{
throw new System.Exception("Unexpected MessageQueue exception", smmqe);
}
}
catch(System.Exception se)
{
MessageBox.Show(se.GetType().ToString() + ": " + se.Message, "Exception occurred in MQPeekCompletedCallback()");
}
finally
{
if(mq != null)
{
mq.BeginPeek(new TimeSpan(0,1,0));
}
}
}
==============================================================
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Again, asynchronous calls - which you said you used - run in a different thread. How else do you think they are not blocking calls? You invoke the call on a different thread, whether you know it or not (and you really should). What I said about Control.Invoke still applies.
You should read Including Asynchronous Calls[^] in the .NET Framework SDK for more information.
As far as the GDI+ error, when and where in your code do you see it? You should step through and determine where it's being thrown. If it's not, it's probably thrown from the message pump I mentioned before. Certain errors like that are difficult to trace.
Microsoft MVP, Visual C#
My Articles
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Heath,
Thank you for your assistance. I was aware (from a previous problem that you helped me with on CodeProject) the need for Control.Invoke and multiple threads. I was not aware that the asynchronous callback was implicitly its own thread althought this makes sense now. I do need to read "Including Asnych Calls" in .NET SDK... thanks for the link.
@@@@ 1 More question @@@@@
I guess my job as a programmer is not to know at compile time which thread a given method is executing in and, hence, the need for InvokeRequired and Control.Invoke. Finally, my question. Why can't .NET make the "InvokeREquired" check for?
Granted programmer's would get "generic" processing but then they could override the default .NET processing. Or am I missing something here?
TIA,
Matt
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For synchronous execution in a single-threaded application, that would be a complete waste of time.
You could something like I did, however. Have a method that accepts some information about what method you want to call or what property you want to get/set. Also accept a delegate (Delegate - nothing specific). That method would check InvokeRequired and conditionally execute that Delegate either using Control.Invoke (to execute it on the creation thread) or Delegate.Invoke (to execute it on the calling thread).
Microsoft MVP, Visual C#
My Articles
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I ran into a similar problem before. I understood that I had to update the control on the thread that created it and I wrote a queue mechanism to do this. However, I was surprised to see that the asynchronous callback from the event ran on different thread. (Now its obvious but it was unclear to me then.) Try setting the thread name property on the form where you create your datagrid. Then do a simple debug assert against this thread name property in the asynchronous callback to ensure that you are updating your datagrid on the correct thread. This will at least tell you whether or not your async callback is on the same thread. (My guess is that it isn’t but I’m still new to this .Net stuff)
//Place this in the form init
Thread.CurrentThread.Name ="UI thread";
//Place this in the async callback
Debug.Assert(Thread.CurrentThread.Name =="UI thread");
Heath’s recommendation about Invoke is sound advice.
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Is there an equivalent to sprintf in C#? Basically I have some C# "value types" (floats, decimals) that I would like to format into a string variable. Also, I have a DateTime variable that I would like to format into a string variable. What is the best way to do this?
Thanks.
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See String.Format in the .NET Framework SDK documentation. Many types - like the primitive types - implement IFormatProvider and have an overloaded ToString method which accepts the same format specifiers as you'd pass in String.Format:
double d = 1.5;
string a = string.Format("{0:C}", d);
string b = d.ToString("C");
Console.WriteLine(a == b); Other methods like StringBuilder.AppendFormat and Console.WriteLine can also accept format specifiers with parameter indexes.
For more information, also see my article, Custom String Formatting in .NET[^]. I also mention several reasons why String.Format and all the classes, methods, and interfaces that comprise formatting in .NET are better than any printf-like function.
Microsoft MVP, Visual C#
My Articles
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Thanks Heath,
You beat me to my post below. 
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I think I got it. . . Its done by passing args to the ToString() method.
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You still might want to look at what I wrote. Calling the overloaded ToString to format types isn't always the best way.
If you look at my article about custom format providers, you might notice why. When using String.Format (or similar methods), you can localize your application much easier because you can localize the entire format string and not have to worry about parameter order since you specify the parameter indexes in the format string. If all you're doing is printing a Type (like some primitive), then using ToString is fine. You should also keep in mind that the overridden ToString uses a well-defined output (typically the same as the "G" format specifier, although this is only a guidelines).
I also have several links in my article to more information in .NET Framework SDK. No, I'm not trying to market my article, I just don't feel like copying and pasting all the links. There's just a lot more power in string formatting within .NET and it's worth understanding.
Microsoft MVP, Visual C#
My Articles
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Heath,
I just read your article; thanks for posting it. It brings together all the MSDN articles that I had read and the ones that I missed and it cuts straight to the point.
Thanks again.
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If somebody could make sense of the behaviour of the following code, I'd be really happy.
On the second line, either #define CRASH to have it crash or don't to have it, well, not crash.
Then just pick the menu items sequentially from 1 to 4.
The only difference is that in the crashing version, a UserControl is added as a control to a Panel instead of directly to a Form...
After closing the form created in step 4, the application freezes, sometimes terminates with an ObjectDisposedException ...
Cheers,
Gunther 
------------- CODE STARTS HERE -------------
// define "CRASH" to have it crash when you go from 1 to 4 ...
#define CRASH
using System;
namespace TestApp
{
/// <summary>
/// Summary description for Form1.
/// </summary>
public class Form1 : System.Windows.Forms.Form
{
[STAThread]
static void Main()
{
System.Windows.Forms.Application.Run(new Form1());
}
private System.Windows.Forms.Panel panel1;
public Form1()
{
this.panel1 = new System.Windows.Forms.Panel();
this.SuspendLayout();
//
// Menu
//
this.Menu = new System.Windows.Forms.MainMenu();
System.Windows.Forms.MenuItem mi = new System.Windows.Forms.MenuItem("Crashing!?");
this.Menu.MenuItems.Add(mi);
mi = new System.Windows.Forms.MenuItem("1. Create Control");
mi.Click += new EventHandler(this.Create_Click);
this.Menu.MenuItems[0].MenuItems.Add(mi);
mi = new System.Windows.Forms.MenuItem("2. Display Dialog");
mi.Click += new EventHandler(this.Dialog_Click);
this.Menu.MenuItems[0].MenuItems.Add(mi);
mi = new System.Windows.Forms.MenuItem("3. Destroy Control");
mi.Click += new EventHandler(this.Destroy_Click);
this.Menu.MenuItems[0].MenuItems.Add(mi);
mi = new System.Windows.Forms.MenuItem("4. Display Dialog");
mi.Click += new EventHandler(this.Dialog_Click);
this.Menu.MenuItems[0].MenuItems.Add(mi);
mi = new System.Windows.Forms.MenuItem("-");
this.Menu.MenuItems[0].MenuItems.Add(mi);
mi = new System.Windows.Forms.MenuItem("Quit");
mi.Click += new EventHandler(this.Quit_Click);
this.Menu.MenuItems[0].MenuItems.Add(mi);
//
// panel1
//
this.panel1.AutoScroll = true;
this.panel1.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D;
this.panel1.Dock = System.Windows.Forms.DockStyle.Fill;
this.panel1.Location = new System.Drawing.Point(0, 0);
this.panel1.Name = "panel1";
this.panel1.Size = new System.Drawing.Size(464, 326);
this.panel1.TabIndex = 1;
//
// Form1
//
this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
this.ClientSize = new System.Drawing.Size(464, 326);
this.Controls.Add(this.panel1);
this.Name = "Form1";
this.Text = "Form1";
this.ResumeLayout(false);
#if (CRASH)
#else
this.panel1.Hide();
#endif
}
private void Quit_Click(object sender, System.EventArgs e)
{
this.Close();
}
private void Destroy_Click(object sender, System.EventArgs e)
{
#if (CRASH)
for (int i = this.panel1.Controls.Count - 1; i >= 0; i--)
{
if (this.panel1.Controls[i].GetType() == typeof(System.Windows.Forms.UserControl))
this.panel1.Controls.RemoveAt(i);
}
#else
for (int i = this.Controls.Count - 1; i >= 0; i--)
{
if (this.Controls[i].GetType() == typeof(System.Windows.Forms.UserControl))
this.Controls.RemoveAt(i);
}
#endif
}
private void Create_Click(object sender, System.EventArgs e)
{
System.Windows.Forms.UserControl umc = new System.Windows.Forms.UserControl();
umc.Controls.Add(new System.Windows.Forms.TextBox());
#if (CRASH)
this.panel1.Controls.Add(umc);
#else
this.Controls.Add(umc);
#endif
}
private void Dialog_Click(object sender, System.EventArgs e)
{
// show dialog
System.Windows.Forms.Form d = new System.Windows.Forms.Form();
d.ShowDialog();
d.Dispose();
}
}
}
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Reason, I cannot give, but fix I can:
Replace:
if (this.panel1.Controls[i].GetType() == typeof(System.Windows.Forms.UserControl))
this.Controls.RemoveAt(i);
With:
if (this.panel1.Controls[i].GetType() == typeof(System.Windows.Forms.UserControl))
{
this.panel1.Controls[i].Controls.Clear();
this.panel1.Controls.RemoveAt(i);
}
Ran into this a while back....
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Thanks je,
your suggestions works.
However, meanwhile I also found that simply calling a Dispose() instead of the RemoveAt() also works.
I also realized that my original problem was twofold - the one from the posted source, the other, giving the DisposeException only occurs when a LinkLabel control was part of a GroupBox on a UserControl ...
Well, I just avoid having those in GroupBoxes for now ...
Regards,
Gunther
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I while ago a link was posted in this forum to a site that contains details of the specification of all the DllImport attribute specifications in order to P/Invoke them correctly. Unfortunately I've not been able to find it. Does anyone have the link?
"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar
The Second EuroCPian Event will be in Brussels on the 4th of September
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Many thanks for the link. It has been most useful... So useful in fact that I've added it to my signature so everyone will know about it! 
"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar
The Second EuroCPian Event will be in Brussels on the 4th of September
Can't manage to P/Invoke that Win32 API in .NET? Why not do interop the wiki way!
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Got a "crash" in the designer. I have a custom form that has almost no code in it and works fine, both in code and in the designer. I create a new inherited form from that custom form. The inherited form *immediately* (i.e. I make no changes from the code that is generated) shows the following error when I try to open it in the designer: "Object reference not set to an instance of an object".
Note that the inherited form and the base form are NOT in the same assembly, but the inherited form's assembly DOES reference the base form's assembly.
Also note that the code compiled just fine, and runs fine when I create an instance of the inherited form.
Any takers?
~Steve
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Where the classes are (i.e., in what assembly) doesn't matter so long as the assemblies are resolvable by the project that use types in those assemblies. This could be your problem.
Design-time components should typically be installed into the GAC for this very reason. See How the Runtime Locates Assemblies[^] in the .NET Framework SDK for more information.
You should also consider debugging VS.NET. Yes, that's right. Open another instance of VS.NET and either attach to the former devenv.exe process or start a new one. Open your projects (works best with debug builds, of course) and try designing your components. It's fairly common to do so when extending the design-time capabilities of your components.
Microsoft MVP, Visual C#
My Articles
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Heath, thanks for the reply. I'll give it a go. Is there anything I should know about installing things into the GAC? If my base form and inherited form are both changing frequently, should I just put a post-build event to install dll's into the GAC after each build? I'm guessing that after a while I'll end up with a ton of useless versions of my dll in the GAC that way. Should I make "uninstall previous" and "install current" post-build events?
Again, thanks for your help...
~Steve
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