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Delphi Across Platforms
How do I make a DLL in Delphi to use in C#?
Posted: 12 Dec 10 (Edited 2 Jan 11)
This is what I've learned today making a DLL in Delphi 7 to use in an ASP.NET 4.0 Website in C#. I'm brand new to C# and am basically teaching myself, all my previous knowledge has been in just Delphi and SQL.
This DLL is specifically one single function called to validate an encrypted string using one of my pre-built encryption objects in Delphi. I'm building a website which utilizes a SQL database from a larger Delphi package of mine, which I have specific encryption techniques I needed to use in the website.
Some of the code is specific to my project, but you can clear the function and change it accordingly.
Delphi 7: JDEncr.dll
Create a new DLL by going to File > New > Other... > New Tab > DLL Wizard
Encryption in '..\JDCommon\Encryption.pas';
//Pre-made encryption unit
//Note: use PChar and not String, and Bool, not Boolean
//stdcall goes at the end of each declaration
function CompareStrings(PlainText, EncryptedText: PChar;
EncType: Integer; CaseSensitive: Bool): Bool; stdcall;
Enc:= TEncType.Create(EncType, 1);
Result := False;
S:= DecryptString(EncryptedText, Enc);
if CaseSensitive then begin
if S = PlainText then
end else begin
if UpperCase(S) = UpperCase(PlainText) then
//exports section goes at end of unit before the begin/end.
//List everything you want to export, just like in the uses
Save this DLL in the 'bin' folder of the website's project.
C#: Class JDEncr.cs
In Visual Studio 2010, right-click the project's root in the Solution Explorer > Add > New Item... > C Sharp > Web > Class
Reminder: C# is case-sensitive
//use InteropServices to use DllImport
public class JDEncr
//Uses Ansi CharSet
//Uses StdCall CallingConvention (like in Delphi)
//uses String instead of PChar
//Parameters recognize types only, and names can differ from original function in DLL
[DllImport("JDEncr.dll", CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Ansi)]
public static extern bool CompareStrings(String PlainText, String EncryptedText, int EncType, bool CaseSensitive);
C#: Utilization of JDEncr
bool P = JDEncr.CompareStrings(EnteredPassword, RegisteredPassword, EncryptionType, true);
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