Multiple ByVal type declarations - vb.net

Question

I have
Private Declare Function ReadProcessMemory Lib "kernel32" Alias "ReadProcessMemory" (ByVal hProcess As Integer, ByVal lpBaseAddress As Integer, ByRef lpBuffer As Integer, ByVal nSize As Integer, ByRef lpNumberOfBytesWritten As Integer) As Integer
But I also need
Private Declare Function ReadProcessMemory Lib "kernel32" Alias "ReadProcessMemory" (ByVal hProcess As Integer, ByVal lpBaseAddress As Integer, ByRef lpBuffer As Single, ByVal nSize As Integer, ByRef lpNumberOfBytesWritten As Integer) As Integer
And some other variations. So, as in the example above, lpBuffer as Single instead of Integer. How can I achieve this?
UPDATE: Alrighty, now I'm doing this:
Imports System.Math
Imports System.Threading
Imports System.Runtime.InteropServices
Public Class Form1
'Declare ReadProcessMemory with lpBuffer As IntPtr
Private Declare Function ReadProcessMemory Lib "kernel32" Alias "ReadProcessMemory" (ByVal hProcess As Integer, ByVal lpBaseAddress As Integer, ByRef lpBuffer As IntPtr, ByVal nSize As Integer, ByRef lpNumberOfBytesWritten As Integer) As Integer
'This is the function I am now having trouble with
Public Function memfloat(ByVal address As Long, ByVal processHandle As IntPtr)
Dim floatvalueinmemory As Single
ReadProcessMemory(processHandle, address, floatvalueinmemory, 4, 0)
Dim letstryagain As Single 'floatvalueinmemory didn't give the desired result, so going to try to TryParse
Single.TryParse(floatvalueinmemory, letstryagain)
Return CStr(letstryagain) 'returns the same result as floatvalueinmemory did
End Function
End Class
Partial Public Class NativeMethods
<DllImport("user32.dll")> _
Public Shared Function ReadProcessMemory(ByVal hProcess As System.IntPtr, ByVal lpBaseAddress As IntPtr, ByVal lpBuffer As System.IntPtr, ByVal nSize As UInteger, ByVal lpNumberOfBytesRead As IntPtr) As Boolean
End Function
End Class
The memfloat function used to return something like "-75,48196", now it returns something like "-1,012555E+09" (the actual values don't match, just using these as an example), this is why I wanted to declare multiple times in the first place.. how do I convert from the IntPtr to a Single ?
What does work is:
Public Function memstring(ByVal address As Long, ByVal length As Int32, ByVal processHandle As IntPtr)
Dim stringinmemory As Long
Dim ret1 As Byte() = Nothing
Dim tStr(length) As Char
Dim retStr As String = ""
For i As Int32 = 0 To length - 1
ReadProcessMemory(processHandle, address + i, stringinmemory, 1, 0)
ret1 = BitConverter.GetBytes(stringinmemory)
tStr(i) = System.Text.Encoding.ASCII.GetString(ret1) : retStr += tStr(i)
Next
Return retStr
End Function
This correctly returns the memory value as string. So yeah, now it's just the Single that's causing issues.

Answer 1

You are using the Alias keyword anyway, so take advantage of it:
Private Declare Function ReadProcessMemoryInt Lib "kernel32" _
Alias "ReadProcessMemory" (ByVal hProcess As Integer, _
ByVal lpBaseAddress As Integer, _
ByRef lpBuffer As Integer, _
ByVal nSize As Integer, _
ByRef lpNumberOfBytesWritten As Integer) As Integer
Private Declare Function ReadProcessMemorySingle Lib "kernel32" _
Alias "ReadProcessMemory" (ByVal hProcess As Integer, _
ByVal lpBaseAddress As Integer, _
ByRef lpBuffer As Single, _
ByVal nSize As Integer, _
ByRef lpNumberOfBytesWritten As Integer) As Integer
The name you give to the function can be arbitrary. Only the Alias name must match the name in the library. In your code, you can refer to ReadProcessMemoryInt and ReadProcessMemorySingle (or whatever name you chose).
(Note: I didn't check whether you are actually using the API correctly, I've just answered your question about how to define the same API function twice with different signatures.)

Answer 2

I fired up the P/Invoke Interop Assistant tool (link), found ReadProcessMemory and generated the signature in vb.net as:
Partial Public Class NativeMethods
'''Return Type: BOOL->int
'''hProcess: HANDLE->void*
'''lpBaseAddress: LPCVOID->void*
'''lpBuffer: LPVOID->void*
'''nSize: SIZE_T->ULONG_PTR->unsigned int
'''lpNumberOfBytesRead: SIZE_T*
<System.Runtime.InteropServices.DllImportAttribute("kernel32.dll", EntryPoint:="ReadProcessMemory")> _
Public Shared Function ReadProcessMemory(<System.Runtime.InteropServices.InAttribute()> ByVal hProcess As System.IntPtr, <System.Runtime.InteropServices.InAttribute()> ByVal lpBaseAddress As System.IntPtr, ByVal lpBuffer As System.IntPtr, ByVal nSize As UInteger, ByVal lpNumberOfBytesRead As System.IntPtr) As <System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.Bool)> Boolean
End Function
End Class
So the bufffer is IntPtr that you need to convert into an array of various types. I suggest you look into the Marshal class and its static methods. Also here are links to possible relevant articles SO link,url 1,url 2. Translation from c# to vb.net may be needed. I also noticed on these online examples that the function definition can be overloaded (which surprised me).