Visual Basic Concepts

Converting C Declarations to Visual Basic

The procedures in DLLs are most commonly documented using C language syntax. To call these procedures from Visual Basic, you need to translate them into valid Declare statements and call them with the correct arguments.

As part of this translation, you must convert the C data types into Visual Basic data types and specify whether each argument should be called by value (ByVal) or implicitly, by reference (ByRef). The following table lists common C language data types and their Visual Basic equivalents for 32-bit versions of Windows.

C language data type In Visual Basic declare as Call with
ATOM ByVal variable As Integer An expression that evaluates to an Integer
BOOL ByVal variable As Long An expression that evaluates to a Long
BYTE ByVal variable As Byte An expression that evaluates to a Byte
CHAR ByVal variable As Byte An expression that evaluates to a Byte
COLORREF ByVal variableAs Long An expression that evaluates to a Long
DWORD ByVal variableAs Long An expression that evaluates to a Long
HWND, HDC, HMENU, etc. (Windows handles) ByVal variableAs Long An expression that evaluates to a Long
INT, UINT ByVal variableAs Long An expression that evaluates to a Long
LONG ByVal variableAs Long An expression that evaluates to a Long
LPARAM ByVal variable As Long An expression that evaluates to a Long
LPDWORD variable As Long An expression that evaluates to a Long
LPINT, LPUINT variable As Long An expression that evaluates to a Long
LPRECT variable As type Any variable of that user-defined type
LPSTR, LPCSTR ByVal variable As String An expression that evaluates to a String
LPVOID variable As Any Any variable (use ByVal when passing a string)
LPWORD variable As Integer An expression that evaluates to an Integer
LRESULT ByVal variable As Long An expression that evaluates to a Long
NULL As Any or
ByVal variable As Long
ByVal Nothing orByVal 0&orvbNullString
SHORT ByVal variable As Integer An expression that evaluates to an Integer
VOID Sub procedure Not applicable
WORD ByVal variable As Integer An expression that evaluates to an Integer
WPARAM ByVal variable As Long An expression that evaluates to a Long