Question

在C#中，怎么传递Delphi生成的dll的string类型数据。

Answer 1

delphi创建DLL的时候，工程单元都会有个提示，意思就是，delphi的string类型是delphi自己定义的类型，不是广域的string,具体百度下《delphi中string与pchar的区别》
方法一：如果你确定要在DLL中使用string作为参数传递类型，必须在第一个引用中引用ShareMem单元（好象仅限delphi自己调用,以前我用C#调用的时候还是会老报错）;
方法二：将string类型改为pchar、ShortString 。
一般delphi的DLL都是用pchar来替换string的。
Important note about DLL memory management: ShareMem must be the
first unit in your library's USES clause AND your project's (select
Project-View Source) USES clause if your DLL exports any procedures or
functions that pass strings as parameters or function results. This
applies to all strings passed to and from your DLL--even those that
are nested in records and classes. ShareMem is the interface unit to
the BORLNDMM.DLL shared memory manager, which must be deployed along
with your DLL. To avoid using BORLNDMM.DLL, pass string information
using PChar or ShortString parameters.

Answer 2

DELPHI里的是这样的：
function ArrayTst(strAry:Array of PChar):PChar;stdcall;
var
i:integer;
strAdd:string;
begin
strAdd:= ' ';
for i:=low(strAry) to High(strAry) do
begin
strAdd:=strAdd+strAry[i]
end;
Result:=PChar(strAdd);
end;

C#里是这样的：
声明：
[DllImport( "ArrayTest1.dll ", EntryPoint = "ArrayTst ", CharSet = CharSet.Ansi,CallingConvention=CallingConvention.StdCall)]
public extern static string ArrayTst(string[] ary);

调用：
string[] arytst=new string[]{ "a1 ", "b2 ", "c3 "};
TextBox1.Text=ArrayTst(arytst);
但报出System.NullReferenceException: 未将对象引用设置到对象的实例