import C# Dll in delphi 10.4

[msi1393 0]

Hello I need to use of C# Dll in my Delphi program

i use of delphi 10.4
is this possible?
 If there is, please explain me step by step

Edited April 26, 2024 by msi1393

[David Heffernan 2415]

There are lots of different ways to do this depending on what the dll offers. Nobody can give you any steps without knowing how the dll exposes its functionality. 

[PeterBelow 250]

17 hours ago, msi1393 said:

Hello I need to use of C# Dll in my Delphi program

i use of delphi 10.4
is this possible?
 If there is, please explain me step by step

If the DLL is COM-enabled you can use the Component -> Import component dialog from the IDE main menu:

 

A pure .NET assembly without COM support cannot be used from Delphi with the tools available out of the box, but there are 3rd-party libraries available, some freeware.  A google search for "host the .net framework in delphi" turns up this for example. I have no personal experience with such libraries.

 

[msi1393 0]

Hello
Thank you for your guidance
I did this but it didn't work

[David Heffernan 2415]

10 hours ago, msi1393 said:

I did this but it didn't work

We still don't know anything about your dll. When I said that nobody can give you any step by step guides without knowledge of what the dll is, I stand by that. I mean, we could write you lots of hypotheticals. You've got one above. But how about you put some effort in and find out what this dll offers. 

[eivindbakkestuen 55]

Use C# to create an intermediate DLL that loads the existing DLL, and exports the methods you need on the Delphi side, using types and calling conventions compatible with Delphi.

[msi1393 0]

Hello
And thank you for your guidance
I tried every guide I could find but it didn't work.
Actually, I want to do the following code in Delphi
that I can use a software implemented with #C
I am attaching the text file of the class related to the dll created in C#

Class1.cs

[David Heffernan 2415]

Rather than linking to files, please show the code inline, formatted 

[Die Holländer 83]

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

procedure Encrypt(sr: PAnsiChar; key: PAnsiChar; var encryptedText: PAnsiChar); stdcall; external 'YourDLLName.dll';
procedure Decrypt(sr: PAnsiChar; key: PAnsiChar; var decryptedText: PAnsiChar); stdcall; external 'YourDLLName.dll';

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
  inputText, key, encryptedText, decryptedText: PAnsiChar;
begin
  inputText := 'Hello World';
  key := '12345678';

  // Encrypt
  Encrypt(inputText, key, encryptedText);
  ShowMessage('Encrypted Text: ' + encryptedText);

  // Decrypt
  Decrypt(encryptedText, key, decryptedText);
  ShowMessage('Decrypted Text: ' + decryptedText);
end;

end.

 

[JonRobertson 81]

12 hours ago, Die Holländer said:

procedure Encrypt(sr: PAnsiChar; key: PAnsiChar; var encryptedText: PAnsiChar); stdcall; external 'YourDLLName.dll';

procedure Decrypt(sr: PAnsiChar; key: PAnsiChar; var decryptedText: PAnsiChar); stdcall; external 'YourDLLName.dll';

That would work for a DLL that contains native code and uses ANSI char based null-terminated strings.

 

The code posted is C# code, using a .NET System.String class "Representing text as a sequence of UTF-16 code units"

 

The DLL generated will be a .NET assembly containing managed code, not native code. As Peter mentioned earlier, either the DLL has to be written & compiled to support COM interop

https://blogs.embarcadero.com/using-a-net-assembly-via-com-in-delphi/

https://www.blong.com/Conferences/BorCon2004/Interop2/COMNetInterop.htm#CCW

 

or the Delphi application that loads the DLL has to host the CLR before the DLL is loaded.

https://stackoverflow.com/questions/2048540/hosting-clr-in-delphi-with-without-jcl-example

https://stackoverflow.com/questions/258875/hosting-the-net-runtime-in-a-delphi-program

https://en.delphipraxis.net/topic/1744-net-runtime-library-for-delphi/

https://adamjohnston.me/delphi-dotnet-interop-with-jvcl/

 

"Explain step by step" isn't possible, as there are a lot of factors to consider. I suspect this is why there are commercial libraries that do this.

https://www.remobjects.com/hydra/

https://www.crystalnet-tech.com/

https://www.atozed.com/crosstalk/

There was a library called Managed-VCL, which can be found online. But the website vanished a while back.

 

[Eric H 0]

A little late to the conversation, but might help future people.

 

Sample code I used with Delphi to interface with a C# .Net DLL that included AWS DynamoDB using the C# AWSSDK.DynamoDBv2 package.  I wanted to receive a class object or send a class object to C#, so I had to deserialize/serialize JSON to do this.  In Delphi I call RegistrationLoad or RegistrationUpdate, which in turn deals with the C# DLL.

 

Delphi:

function DllRegistrationLoad(pRegCode: String): PWideChar; stdcall; external 'MyDllFunctions.dll';
function DllRegistrationUpdate(pRegistrationJson: String): Boolean; stdcall; external 'MyDLLFunctions.dll';

function TAwsDynamoDBQueryDLL.RegistrationLoad(const pRegCode: String): TRegistration;
begin
  Result := nil;
  var vDllResult := DllRegistrationLoad(pRegCode);
  try
    if vDllResult <> '' then
      Result := TJson.JsonToObject<TRegistration>(vDllResult);
  finally
    CoTaskMemFree(vDllResult);
  end;
end;
        
function TAwsDynamoDBQueryDLL.RegistrationUpdate(var pRegistration: TRegistration): Boolean;
begin
  var vReg := TJsonAWSRegistration.Create(pRegistration);
  try
    var vJson := TJson.ObjectToJsonString(vReg);
    Result := DllRegistrationUpdate(vJson);
  finally
    FreeAndNil(vReg);
  end;
end;
        

C# .NET:

        [DllExport(CallingConvention = CallingConvention.StdCall)]
        [return: MarshalAs(UnmanagedType.LPWStr)]
        public static string DllRegistrationLoad([MarshalAs(UnmanagedType.LPWStr)] string regCode)
        {
            var registration = new RegistrationModel();
            ...
            var jsonSettings = new JsonSerializerSettings()
            {
                DateFormatString = "yyyy-MM-dd"
            };
            return JsonConvert.SerializeObject(registration, jsonSettings);
        }

        [DllExport(CallingConvention = CallingConvention.StdCall)]
        public static bool DllRegistrationUpdate([MarshalAs(UnmanagedType.LPWStr)] string registrationJson)
        {
            var registration = JsonConvert.DeserializeObject<RegistrationModel>(registrationJson);
            ...
            return true;
        }

 

[ertank 29]

On 4/29/2024 at 3:48 PM, msi1393 said:

Hello
And thank you for your guidance
I tried every guide I could find but it didn't work.
Actually, I want to do the following code in Delphi
that I can use a software implemented with #C
I am attaching the text file of the class related to the dll created in C#

Class1.cs

You do not need to use the DLL. You already have complete DLL code as far as I can tell. I think it is possible to convert that code to Delphi.

I cannot be sure about the details of C# encryption method. It seems like DES, CBC and PCKS#7 padding. You need to confirm that information.

Once you have all details, there are several free encryption libraries available for Delphi which can help you do the same directly in your project without any need for a DLL.

You can install LockBox from GetIt as an example. There are other alternatives and you may want to check some of them.

In case you are using older versions of Delphi like Delphi 7, you can still build your own DLL using a recent version in case you are not able to use the cryptography library in your Delphi version.

Nowadays there is a lot of AI use. They can also help you convert that C# code into Delphi. if you choose to do it that way just make sure that final code is actually correct.

[Eric H 0]

On 4/16/2025 at 12:01 PM, Eric H said:

A little late to the conversation, but might help future people.

 

Sample code I used with Delphi to interface with a C# .Net DLL that included AWS DynamoDB using the C# AWSSDK.DynamoDBv2 package.  I wanted to receive a class object or send a class object to C#, so I had to deserialize/serialize JSON to do this.  In Delphi I call RegistrationLoad or RegistrationUpdate, which in turn deals with the C# DLL.

 

Delphi:

function DllRegistrationLoad(pRegCode: String): PWideChar; stdcall; external 'MyDllFunctions.dll';
function DllRegistrationUpdate(pRegistrationJson: String): Boolean; stdcall; external 'MyDLLFunctions.dll';

function TAwsDynamoDBQueryDLL.RegistrationLoad(const pRegCode: String): TRegistration;
begin
  Result := nil;
  var vDllResult := DllRegistrationLoad(pRegCode);
  try
    if vDllResult <> '' then
      Result := TJson.JsonToObject<TRegistration>(vDllResult);
  finally
    CoTaskMemFree(vDllResult);
  end;
end;
        
function TAwsDynamoDBQueryDLL.RegistrationUpdate(var pRegistration: TRegistration): Boolean;
begin
  var vReg := TJsonAWSRegistration.Create(pRegistration);
  try
    var vJson := TJson.ObjectToJsonString(vReg);
    Result := DllRegistrationUpdate(vJson);
  finally
    FreeAndNil(vReg);
  end;
end;
        

C# .NET:

        [DllExport(CallingConvention = CallingConvention.StdCall)]
        [return: MarshalAs(UnmanagedType.LPWStr)]
        public static string DllRegistrationLoad([MarshalAs(UnmanagedType.LPWStr)] string regCode)
        {
            var registration = new RegistrationModel();
            ...
            var jsonSettings = new JsonSerializerSettings()
            {
                DateFormatString = "yyyy-MM-dd"
            };
            return JsonConvert.SerializeObject(registration, jsonSettings);
        }

        [DllExport(CallingConvention = CallingConvention.StdCall)]
        public static bool DllRegistrationUpdate([MarshalAs(UnmanagedType.LPWStr)] string registrationJson)
        {
            var registration = JsonConvert.DeserializeObject<RegistrationModel>(registrationJson);
            ...
            return true;
        }

 

I forgot to mention that you need to include the package "UnmanagedExports by Robert Giesecke" for the C# project.