Migrate function C++ with pointers to C#

Question

I have a function in C++ that returns pointer values​​:

fPosFirst( int &aId, char *aNname, char *aDirectory );

My syntax in c# is:

fPosFirst(ref int aId,  String aNname,  String aDirectory);

the function returns the id but not the string parameters that anyone knows?

Answer 1

If you want the parameters to be used for returning values then mark them as ref or out .

Eg

fPosFirst(ref int aId,  out string aNname,  out string aDirectory);

Answer 2

Assuming that the native function does not "return pointers" but writes characters to the memory locations specified by aNname and aDirectory, you should be able to pass a StringBuilder with a proper capacity to the native function:

void fPosFirst(ref int aId, StringBuilder aNname, StringBuilder aDirectory);

Usage:

var aId = 0;
var aNname = new StringBuilder(260);
var aDirectory = new StringBuilder(260);

fPosFirst(ref aId, aNname, aDirectory);

Answer 3

如果要在方法内分配给它们，并使这些值在方法外可用out则需要使字符串参数为ref或out 。

Answer 4

You need to use out keyword before parameters names ( example ). But actually this is not good practice in C#