[Today's programming diary, using a VC-compiled DLL instance in VB]

2003-12-3
Today, like a book, I used VC to compile a dynamic link library (DLL) --. DLL, then copy it to the Windows/system/directory, and then create a vbprogram, and declare a in the program. the add () function in DLL implements the addition operation of two integer numbers.
The implementation process is as follows:
1. Create a DLL
Open VC and create an API-Based DLL.

---- 1. In file-> New-> projects, select "Win32 dynamic-Link Library", enter "A" in project name, and press OK.
---- 2. In file-> New-> files, select C ++ source file, enter a. cpp in file, and press OK.
---- 3. In file-> New-> files, select the text file, enter a. h In file, and press OK.
---- 4. In file-> New-> files, select the text file, enter a. Def in file, and press OK.

---- 5. source file:

Code

//--------------------------- // A. cpp # Include <Windows> Winapi int add (int A, int B) {Return (A + B ); } //--------------------------- // A. h Winapi int add (int A, int B ); //--------------------------- // A. Def Library "A"; specifies the DLL name Description 'a Windows dynamic link library' ; Describes the usage of DLL (this sentence is optional) Exports add; Name of the export Function

------ 6. compile it into a. dll
------ 7. Copy A. DLL to the Windows/system/directory

2. Create a vbprogram
In form1, enter

Code

Option explicit Private declare function add lib "A. dll" (byval A as integer, byval B as integer) as integer Private sub commandementclick () Text3.text = STR (add (Val (text1.text), Val (text2.text ))) End sub

The program interface is as follows:

Problems I encountered during programming:
After copying a. DLL to the program directory (I have not copied a. DLL to the Windows/system/directory), run the program and report an error! For example:

Later I copied a. DLL to E: disk

Code

Private declare function add lib ". DLL "(byval A as integer, byval B as integer) change as integer to private declare function add lib" E:/. DLL "(byval A as integer, byval B as integer) as integer

Run the program again!
I don't know why. The book says that the DLL files required for calling a DLL must be in one of the following three directories:

(1) Windows System directory:/Windows/system;

(2) Any directory indicated by path in DOS;

(3) Directory of the program.
I don't know why I encountered an error when I met the third condition? ========================================================== ==========

This evening, I went to the library to read a book and finally understood why the program went wrong in the afternoon.

The main reason is that when you press F5 to execute a program, the program is still in the debugging stage, so it cannot be found.

To a. dll, think of this, I make the program as an application, and finally everything is normal. I am very grateful.

Wei ~
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