I need to send a structure, containing strings, from VB.Net to unmanaged VC++ dll.
In my VB.Net wrapper, there is the function declaration:
Public Declare Ansi Function BDS_CapProc Lib "BDS_TK.dll" _
(ByRef in_cap As CapInput, ByRef outcap_eval As CapOutEval, _
ByRef outcap_annual As CapOutAnnual, ByRef outcap_intermed As CapOutIntermed) As Int16
The CapInput structure is defined as:
<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Unicode)> _
Dim CapCash() As Double
Dim CapInfl() As Double
Dim ProdIncFac() As Double
Dim Pct_Replace As Double
Dim CCA_Rate As Double
Dim Salv_Fac As Double
Dim Rem_Fac As Double
Dim CR_Exp_Fac As Double
Dim PIS_Exp_Fac As Double
Dim Exp_Book_Fac As Double
Dim Exp_Tax_Fac As Double
Dim CFTiming As Int16
Dim OPST_apply As Int16
Dim QPST_apply As Int16
Dim TGET_exempt As Int16
Dim DSP_Treatment As Int16
Dim ComRetYr As Int16
Dim ComRetMth As Int16
Dim Life_Est As Int16
Dim Surv_Curve As Int16
Dim Scenario As Int16
Dim Mthly_Svc As Int16
Dim z_Fill As Int16
Dim Cap_ID As String
Dim Cap_Description As String
When I populate the CapInput structure, the data is good; when I send it to unmanaged code, the data is all corrupt. I have tried other variations of the <MarshalAs(UnmanagedType attribute (LPStr, LPWStr, LPTStr) all with the same reault.
I have tried CharSet:=CharSet.Ansi and CharSet:=CharSet.Auto in the StructLayout attribute. Always the same result.
The unmanaged code is in production, and works fine. It is currently called from Excel VBA. The structure definition is the same as above (except for the MarshalAs part, which is not need when calling from VBA).
I have successfully passed managed structures containing only Doubles and Int16?s to the unmanaged code; no problem there. The other 3 structures in the above call contain no strings. So, I think the strings in the CapInput structure are hanging me up.
Any ideas are appreciated.
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