RichTextBox access error ?

vertigo

Hello
I have some Threads, and they write something to
RichTextBox.Text property. But sometimes i receive error:

************** Exception Text **************
System.NullReferenceException: Object reference not set to an instance
of an object.
at System.Windows.Forms.RichTextBox.EditStreamProc(In tPtr dwCookie,
IntPtr buf, Int32 cb, Int32& transferred)
at System.Windows.Forms.UnsafeNativeMethods.CallWindo wProc(IntPtr
wndProc, IntPtr hWnd, Int32 msg, IntPtr wParam, IntPtr lParam)
at System.Windows.Forms.NativeWindow.DefWndProc(Messa ge& m)
at System.Windows.Forms.Control.DefWndProc(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.TextBoxBase.WndProc(Message& m)
at System.Windows.Forms.RichTextBox.WndProc(Message& m)
at System.Windows.Forms.ControlNativeWindow.OnMessage (Message& m)
at System.Windows.Forms.ControlNativeWindow.WndProc(M essage& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32
msg, IntPtr wparam, IntPtr lparam)

Why ? Is it problem with synchronization: that many threads try to
change Text property at the same time, or what ?
How can i solve this problem ?

Thanx
Michal

Nov 16 '05 #1

Subscribe Post Reply

2095

AlexS

vertigo,

if you access any UI control from threads you might have similar problems.
Most of UI controls are single-threaded by definition and you can safely
access them only from UI thread.

HTH
Alex
"vertigo" <ax***@wp.pl> wrote in message
news:cn**********@nemesis.news.tpi.pl...

Hello
I have some Threads, and they write something to
RichTextBox.Text property. But sometimes i receive error:

************** Exception Text **************
System.NullReferenceException: Object reference not set to an instance
of an object.
at System.Windows.Forms.RichTextBox.EditStreamProc(In tPtr dwCookie,
IntPtr buf, Int32 cb, Int32& transferred)
at System.Windows.Forms.UnsafeNativeMethods.CallWindo wProc(IntPtr
wndProc, IntPtr hWnd, Int32 msg, IntPtr wParam, IntPtr lParam)
at System.Windows.Forms.NativeWindow.DefWndProc(Messa ge& m)
at System.Windows.Forms.Control.DefWndProc(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.TextBoxBase.WndProc(Message& m)
at System.Windows.Forms.RichTextBox.WndProc(Message& m)
at System.Windows.Forms.ControlNativeWindow.OnMessage (Message& m)
at System.Windows.Forms.ControlNativeWindow.WndProc(M essage& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32
msg, IntPtr wparam, IntPtr lparam)

Why ? Is it problem with synchronization: that many threads try to
change Text property at the same time, or what ?
How can i solve this problem ?

Thanx
Michal

Nov 16 '05 #2

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