ButtonBase.IsDefault Property
.NET Framework 4
Gets or sets a value indicating whether the button control is the default button.
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
When the IsDefault property is set to true, the button is the default button for the Form. This means that the button is clicked when the ENTER key is pressed if no other button or any other control that captures the ENTER key has focus.
To specify the default button of a form, set the AcceptButton property of the form to the desired button.
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.