Question

vb中API常数都表示什么意思？

比如Declare Function SendMessage& Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any)
Declare Function SendMessageBynum& Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long)
Declare Function SendMessageByString& Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As String)
说明
调用一个窗口的窗口函数，将一条消息发给那个窗口。除非消息处理完毕，否则该函数不会返回。SendMessageBynum， SendMessageByString是该函数的“类型安全”声明形式
返回值
Long，由具体的消息决定
参数表
参数 类型及说明
hwnd Long，要接收消息的那个窗口的句柄
wMsg Long，消息的标识符
wParam Long，具体取决于消息
lParam Any，具体取决于消息

里面要用到LB_SETHORIZONTALEXTENT 但在API中如何找出？
查找API函数表时，并没有给出呀

Answer 1

其实就是数字，LB_SETHORIZONTALEXTENT = 404，在C的头文件中可以找到

你可以下载一个 API Explorer 软件来查看其值，而且还有许多API的定义，直接复制就可以了,非常方便