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Delphi Across Platforms

How do I make a DLL in Delphi to use in C#? by djjd47130
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


library JDEncr;

  Encryption in '..\JDCommon\Encryption.pas';
  //Pre-made encryption unit

{$R *.res}

//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;
  S: String;
  Enc: TEncType;
  Enc:= TEncType.Create(EncType, 1);
    Result := False;
    S:= DecryptString(EncryptedText, Enc);
    if CaseSensitive then begin
      if S = PlainText then
        Result:= True;
    end else begin
      if UpperCase(S) = UpperCase(PlainText) then
        Result:= True;

//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


using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Runtime.InteropServices;
//use InteropServices to use DllImport

namespace JDWeb
    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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