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Control.CheckForIllegalCrossThreadCalls Property

.NET Framework 4

Gets or sets a value indicating whether to catch calls on the wrong thread that access a control's Handle property when an application is being debugged.

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)
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[BrowsableAttribute(false)]
public static bool CheckForIllegalCrossThreadCalls { get; set; }

Property Value

Type: System.Boolean
true if calls on the wrong thread are caught; otherwise, false.

When a thread other than the creating thread of a control tries to access one of that control's methods or properties, it often leads to unpredictable results. A common invalid thread activity is a call on the wrong thread that accesses the control's Handle property. Set CheckForIllegalCrossThreadCalls to true to find and diagnose this thread activity more easily while debugging.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
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Will NOT raise exceptions outside the debugger by default
>> Note that illegal cross-thread calls will always raise an exception when an application is started outside the debugger.
This is not true, CheckForIllegalCrossThreadCalls defaults to Debugger.IsAttached and can always be overriden.
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