How to call this Delphi function from C#?

Question

i'm having problems calling a delphi function from C# (attempted to read or write protected memory), and was wondering what the correct way of calling the method should be. The Delphi function signature is as follows:

procedure methodToCall(
    aFirstParameter: Widestring; 
    var aSecondParameter: Widestring
    ); stdcall;

What is the correct way of calling this method from C#?

Hi, how are you calling this from C#? with DllImport or with COM interoperability? Did you add the reference? Can we see the C# side as well? — Davide Piras, Mar 15 '11 at 09:52

David Heffernan · Accepted Answer · 2011-03-15T10:34:56.957

8

The WideString is compatible with COM BSTR and so the .net marshaller should be able to consume it quite happily:

[DllImport(@"test.dll")]
private static extern void methodToCall(
    [MarshalAs(UnmanagedType.BStr)]
    string aFirstParameter,
    [MarshalAs(UnmanagedType.BStr)]
    ref string aSecondParameter
);

edited Mar 15 '11 at 10:34

answered Mar 15 '11 at 10:23

David Heffernan

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what would happen if i used [MarshalAs(UnmanagedType.LPStr)] StringBuilder firstParameter ? – oɔɯǝɹ Mar 15 '11 at 10:31
What would be wrong because the Delphi code is written to receive a WideString (aka BSTR) and not an LPStr. I just wrote a DLL to test this and the C# code above works perfectly. – David Heffernan Mar 15 '11 at 10:34
Have you a source for Delphi WideStrings and BSTR being the same? – CodesInChaos Mar 15 '11 at 10:37
1

@CodeInChaos It's stated in the [Delphi documentation](http://docwiki.embarcadero.com/RADStudio/en/String_Types#WideString) – David Heffernan Mar 15 '11 at 11:07

How to call this Delphi function from C#?

1 Answers1