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Visual Basic 6 definition

Declare Function SetClassLong Lib "user32.dll" Alias "SetClassLongA" (ByVal hWnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long

Visual Basic .NET definition

Declare Function SetClassLong Lib "user32" Alias "SetClassLongA" (ByVal hwnd As Integer, ByVal nIndex As Integer, ByVal dwNewLong As Integer) As Integer

C# definition

[DllImport("user32", EntryPoint="SetClassLong")] public static extern int SetClassLongA(int hwnd, int nIndex, int dwNewLong)

Description

SetClassLong sets a single 32-bit value from the information about the window class to which the specified window belongs. This function can also set a 32-bit value within the extra memory area associated with the window class. SetClassLong Replaces the specified 32-bit value at the specified offset into the extra class memory or the WNDCLASSEX structure. System.Windows.Forms.Control.CursorSystem.Windows.Forms.Control.NameSystem.Windows.Forms.Form.BackColorSystem.Windows.Forms.Form.IconSystem.Windows.Forms.Form.MenuSystem.Windows.Forms.Form.CreateParams.ClassStyleSystem.Windows.Forms.Form events

Return Value

If an error occured, the function returns 0 (use GetLastError to get the error code). If successful, the function returns the previous setting of the 32-bit value which was changed.

Parameters

hWnd A handle to a window which belongs to the class to set a property of. nIndex To set a 32-bit value within the class's extra memory, set this to the zero-based offset of the first byte in the 32-bit block to set. Valid values are 0 to the number of bytes of extra memory minus 4, inclusive. To set a 32-bit property of the class, set this to one of the following flags specifying which 32-bit value to set from the window class: GCL_CBCLSEXTRA Set the size in bytes of the extra memory associated with the window class. dwNewLong is the new size of the block. GCL_CBWNDEXTRA Set the size in bytes of the extra memory associated with each window belonging to the window class. dwNewLong is the new size of the block. GCL_HBRBACKGROUND Set the brush used to paint the backgrounds of windows belonging to the class. dwNewLong is a handle to the brush to use. GCL_HCURSOR Set the cursor associated with the class. dwNewLong is a handle to the cursor to use. GCL_HICON Set the icon associated with the class. dwNewLong is a handle to the icon to use. GCL_HICONSM Set the small icon associated with the class. dwNewLong is a handle to the small icon to use. GCL_HMODULE Change the module which registered the class. dwNewLong is a handle to the module to identify as the creator of the class. GCL_MENUNAME Set the string identifying the name of the menu resource associated with the class. dwNewLong is a pointer to the new string. GCL_STYLE Set the window styles associated with the class. dwNewLong is the new value. GCL_WNDPROC Set the WindowProc hook function to use as the window procedure for windows belonging to the window class. dwNewLong is a pointer to the function to use. dwNewLong The 32-bit value to set as something.

Constants

Const GCL_CBCLSEXTRA = -20 Const GCL_CBWNDEXTRA = -18 Const GCL_HBRBACKGROUND = -10 Const GCL_HCURSOR = -12 Const GCL_HICON = -14 Const GCL_HMODULE = -16 Const GCL_MENUNAME = -8 Const GCL_STYLE = -26 Const GCL_WNDPROC = -24

Further Information:

For further information on Windows API functions such as these, and how to use these API's in your C# and VB.NET applications, please refer to the book 'Network programming in .NET' (Buy at Amazon UK) (Buy at Amazon US)

Visual Basic 6 example source code
' Change the icon associated with whatever class window ' Form1 belongs to. Dim hIcon As Long ' handle to the new icon to use Dim retval As Long ' return value ' The icon to use is in C:\MyApp\newicon.ico. hIcon = ExtractIcon(App.hInstance, "C:\MyApp\newicon.ico", 0) ' Set this icon as the new class icon. retval = SetClassLong(Form1.hWnd, GWL_HICON, hIcon) ' set the class's icon, not the window's ' Note that here we can't destroy the icon we extracted because it ' is still in use by the class.
Visual Basic .NET example source code

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