### Translation:
Error message: `error C2440: "static_cast": cannot convert from "void (__thiscall *)" to "LRESULT (__thiscall CWnd::* )(WPARAM, LPARAM)"`
If you encounter the above error during programming, it is highly likely due to issues with message mapping after migrating a project from VC6.0 to VS2005. For example, the complete error message I encountered was:
`error C2440: "static_cast": cannot convert from "void (__thiscall CMouseControlDlg::* )(WPARAM, LPARAM)" to "LRESULT (__thiscall CWnd::* )(WPARAM, LPARAM)"`
The issue in my case occurred with the `OnHotKey` function, which is a custom message handler that I wrote. In VC6.0, it was declared as follows:
```cpp
afx_msg void OnHotHotKey();
```
---
### Explanation of the Problem:
This error occurs because there are differences in how Microsoft Visual C++ 6.0 (VC6.0) and Visual Studio 2005 (VS2005) handle type safety in message maps. Specifically:
1. **Return Type Mismatch**: In VS2005, message handlers for certain Windows messages (such as `WM_HOTKEY`) must return `LRESULT` instead of `void`. This stricter type checking ensures compatibility with the underlying Windows API.
2. **Type Casting Issues**: The `static_cast` used internally by the MFC framework to map message handlers to their respective functions fails when the function signatures do not match exactly.
---
### Solution:
To resolve this issue, you need to modify the declaration of the `OnHotKey` function to match the expected signature in VS2005. Update the function as follows:
#### Original Declaration in VC6.0:
```cpp
afx_msg void OnHotKey();
```
#### Updated Declaration for VS2005:
```cpp
afx_msg LRESULT OnHotKey(WPARAM wParam, LPARAM lParam);
```
Additionally, update the function implementation to return an appropriate value (e.g., `0`):
#### Example Implementation:
```cpp
LRESULT CMouseControlDlg::OnHotKey(WPARAM wParam, LPARAM lParam)
{
// Handle the hotkey event here
// ...
return 0; // Return 0 to indicate success
}
```
Finally, ensure that the message map entry for `OnHotKey` is correctly defined in your class's message map:
```cpp
BEGIN_MESSAGE_MAP(CMouseControlDlg, CDialog)
ON_WM_HOTKEY()
END_MESSAGE_MAP()
```
By making these changes, the function signature will align with the expectations of the MFC framework in VS2005, resolving the `C2440` error.