Call C structure data from C# -


i have make dll dev c++.and want call function. dev c++ code :

//the head file struct sadd { int* aarr; int* barr; int length; }; dllimport int addstruct (struct sadd*); //the c file  dllimport int addstruct (struct sadd* sadd) {//sum aarr , barr , return result.           int sum=0;            int* aarr=sadd->aarr;           int* barr=sadd->barr;          int numarr=sadd->length;                 int i;           for(i=0;i<numarr;i++)           sum+=*(aarr+i);           i=0;           for(i=0;i<numarr;i++)           sum+=*(barr+i);            return sum;        }

in order call addstruct function,i need define struct first.

public struct sadd {     public int[] a;     public int[] b;     public int length; }   [dllimport("dllmain.dll", callingconvention = callingconvention.cdecl)]   public static extern int addstruct(ref sadd sadd);

the code call addstruct function this:

    sadd sadd = new sadd();     sadd.a = new int[4] { 1, 2, 3 ,4};     sadd.b = new int[4] { 1, 2, 3 ,4};     sadd.length=4;     console.writeline("sadd:" + addstruct(ref sadd).tostring());

the result should 20,but 37109984 or other big number. ,i not sure how change code right reusult.maybe need use intptr or other ways??thanks .

at last,i deal problem.just modify code in c#.

  [structlayout(layoutkind.sequential)]   public struct sadd   {       public intptr a;       public intptr b;      public int length;   };             sadd sadd = new sadd();             int[] = new int[4] { 1, 2, 3 ,4};              int[] b = new int[4] { 1, 2, 3 ,4};             sadd.length = 4;             sadd.a = marshal.unsafeaddrofpinnedarrayelement(a, 0);             sadd.b = marshal.unsafeaddrofpinnedarrayelement(b, 0);             console.writeline("sadd:" + dllmainwrapper.addstruct(ref sadd).tostring());

your c code broken.

you cannot compute length of array using sizeof when have pointer first element. can when have "real" array declaration in scope.

so this:

int* aarr=sadd->aarr; int* barr=sadd->barr; int numaarr=sizeof(aarr)/sizeof(int); int numbarr=sizeof(barr)/sizeof(int);

is broken, numarr constant value (1 if pointer size same integer size, otherwise 2 on 64-bit system 32-bit int).


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