File I/O with Windows Forms

Question 1

Normally, you can convert a std::string into a System::String^ quite easily (it's even possible that simply using gcnew String(myPrimoAnnoObj.cognome) will give you a string with the right contents, easily written into the managed stream.

However you appear to have failed to grasp how new works for unmanaged objects: Your code allocates a primo_anno structure dynamically for no reason, before copying its value into the list and leaking the pointer. You also leak the pointers to the unmanaged strings you obtained from the Marshal class.

Are you sure you should be using unmanaged objects? It would be much easier to have everything in a managed System::Collections::Generic::List<> of managed objects...

Added: For writing everything in a file, you can try something like this:

ref class MyClass
{
public:
    String^ cognome;
    String^ nome;
    int voto_diploma;
};

//...

List<MyClass^>^ primo = gcnew List<MyClass^>();

//...

MyClass^ myObj = gcnew MyClass();
myObj->cognome = textBox1->Text;
myObj->nome = textBox2->Text;
myObj->voto_diploma = Convert::ToInt32(textBox35->Text);
primo->Add(myObj);

//...

TextWriter ^tw = gcnew StreamWriter(L"primoAnno.txt", true);
for each(MyClass^ obj in primo)
{
    //You can use any character or string as separator,
    //as long as it's not supposed to appear in the strings.
    //Here, I used pipes.
    tw->Write(obj->cognome);
    tw->Write(L"|");
    tw->Write(obj->nome);
    tw->Write(L"|");
    tw->WriteLine(obj->voto_diploma);
}
tw->Close();

For reading, you can use a function like this:

MyClass^ ParseMyClass(String^ line)
{
    array<String^>^ splitString = line->Split(L'|');
    MyClass^ myObj = gcnew MyClass();
    myObj->cognome = splitString[0];
    myObj->nome = splitString[1];
    myObj->voto_diploma = Convert::ToInt32(splitString[2]);
    return myObj;
}

And for deleting:

TextWriter^ tw = gcnew StreamWriter(L"primoAnno2.txt", true);
TextReader^ tr = gcnew StreamReader(L"primoAnno.txt");
String^ line;
while((line=tr->ReadLine()) != nullptr)
{
    MyClass^ obj = ParseMyClass(line);
    if(obj->cognome != L"cat")
        tw->WriteLine(line);
}
tr->Close();
tw->Close();
File::Delete(L"primoAnno.txt");
File::Move(L"primoAnno2.txt", L"primoAnno.txt");

It may not be the exact code, but it's overall what should work.

Note: If you want your separator to be spaces, and there can be spaces in the strings, things will get a lot more complicated.

Question 2

I have tried to use a generic list..(thanks MSDN).in the comments below there are my dubts..

List<String^>^ primo=gcnew List<String^>();
int mark;

char* str1=(char*)(Marshal::StringToHGlobalAnsi(textBox1->Text)).ToPointer();
char* str2=(char*)(Marshal::StringToHGlobalAnsi(textBox2->Text)).ToPointer();
mark = Convert::ToInt16(textBox35->Text);

//here i add TEXTBOXES to my generic list...not objects of my stl list
primo->Add(textBox1->Text);
primo->Add(textBox2->Text);
primo->Add(textBox35->Text);

TextWriter ^tw = gcnew StreamWriter("primoAnno.txt", true);
for each(String^ prim in primo){
//here i write my string one by one in column..i want them all in a line!how?
                               tw->WriteLine(prim);
                              }

//i also have tried to delete an object..but i dont like the remove..i mean i want all the strings in a line, if i find "cat" for example i want to delete the ENTIRE line..not just "cat"
if(primo->Contains("cat"))tw->WriteLine("ok");primo->Remove("cat");
for each(String^ prim in primo){
                               tw->WriteLine(prim);
                              }
tw->Close();

i make an example of my primoAnno.txt file first time i write(and push the register button) i want this:

cat gae 5

second time i write(and push the register button again) i want this:

cat gae 5

bla bla 1

then, when i remove(if there is "cat" in a line delete that line) i want this:

bla bla 1

hope it s useful. thanks to ones who will reply