.NET (Core and Framework)

IntPtr handle = IntPtr.Zero;

Dave Kreskowiak wrote:

The size of IntPtr changes depending on the proc. So, an IntPtr on a 32-bit system is 32-bits wide and on a 64-bit system is 64-bits wide, automatically.

You don't have al allocate anything. You're just using the pointer as a self-sizing integer.

Luc Pattyn wrote:

here is my theory (still theory since I have not run any of this on Win64):
- for native pointers you really should use IntPtr, and it is not hard to do so.
- Win32 uses 4B pointers, Win64 needs 8B pointers
- you must build for either 32-bit or 64-bit
- on Win64 everything must be consistent (all modules 64-bit is fine, and
all modules 32-bit runs in some compatibility mode, not sure tho)
- IntPtr is a value type that holds either 4B or 8B pointer value
- IntPtr must be initialized, normally you give its value at construction
- a lot of P/Invoke examples are wrong, and use int/uint where it should have
been IntPtr. Most notably SendMessage: lParam, wParam and return value should
be regarded as IntPtr, and cast to int or whatever if and when appropriate.
- correct prototypes would have IntPtr for anything that is or could be a handle
(such as lParam).

Luc Pattyn wrote:

Your problem seems to be you did not initialize handle.

Leslie Sanford wrote:

Actually, I don't think I'm suppose to initialize the handle, rather I should use the out modifier on the IntPtr parameters rather than ref, as I had initially tried

Luc Pattyn wrote:

That depends entirely on the function at hand; you typically need to provide
an IntPtr or be ready to receive one (with "out" keyword).

I don't recall any Win32 function that provides a handle that way, they typically
use the return value (and return zero for error, then you would call GetLastError
for details).

Leslie Sanford wrote:

Does this make sense?

Dim con As OleDbConnection
Dim cmd As OleDbCommand = New OleDbCommand
Dim dataSet As dataSet = Nothing
 
Sub BindGrid()
   Dim oleDbDataAdapter As OleDbDataAdapter = Nothing
   Dim ConnectionString = _
     System.Configuration.ConfigurationSettings.AppSettings(ConConstant.MS_ACCESS_CONNECTION_STRING)
 
   ' Ge the sql query
   Dim SelectQueryText As String = String.Empty
   SelectQueryText = "Select Leave_Code as LeaveCode,Leave_Name as LeaveName,NoOfDays as Days from Leave_Mstr"
   oleDbDataAdapter = New OleDbDataAdapter(SelectQueryText, New OleDbConnection(ConnectionString))
 
   ' Create the data set
   dataSet = New DataSet
 
   ' Fill the data set with the data
   oleDbDataAdapter.Fill(dataSet)
   If (Not oleDbDataAdapter Is Nothing) Then
      oleDbDataAdapter = Nothing
   End If
   
   With dgLeavCrtnLeavDtls
      .DataSource = dataSet
      .DataMember = dataSet.Tables(0).TableName
      .DataBind()
   End With
End Sub
 
Sub tablebind()
   Dim oleDbDataAdapter As OleDbDataAdapter = Nothing
   Dim ConnectionString = _
      System.Configuration.ConfigurationSettings.AppSettings(ConConstant.MS_ACCESS_CONNECTION_STRING)
 
   ' Ge the sql query
   Dim SelectQueryText As String = String.Empty
   SelectQueryText = "Select Leave_Code as LeaveCode,Leave_Name as LeaveName,NoOfDays as Days from Leave_Mstr"
   oleDbDataAdapter = New OleDbDataAdapter(SelectQueryText, New OleDbConnection(ConnectionString))
 
   ' Create the data set
   dataSet = New DataSet
 
   ' Fill the data set with the data
   oleDbDataAdapter.Fill(dataSet)
 
   Dim dh As TableHeaderCell
   Dim dc As DataColumn
   Dim dr As DataRow
 
   For Each dr In dataSet.Tables(0).Rows
      Dim trow As New TableRow
 
      For Each dc In dataSet.Tables(0).Columns
         Dim tcell As New TableCell
         tcell.Controls.Add(New LiteralControl(dr(dc.ColumnName).ToString))
         trow.Cells.Add(tcell)
      Next
   Next
End Sub