Question

I tried to extend a listbox by adding a couple functions. I get an error ( error C2144: syntax error : ‘Extended_ListBox’ should be preceded by ‘:’). Would anyone please teach me how to fix it? I went to the line which VC++ said there was the error, but I had no clue why the constructor had an error.

    using namespace System;
using namespace System::ComponentModel;
using namespace System::Collections;
using namespace System::Windows::Forms;
using namespace System::Data;
using namespace System::Drawing;
using namespace System::Collections;
using namespace System::Collections::Generic;

#include <stdio.h>
#include <stdlib.h>
#using <mscorlib.dll>


public ref class Extended_ListBox: public ListBox{  

    public Extended_ListBox(array<String ^> ^ textLineArray, int counter){
        textLineArray_store = gcnew array<String ^>(counter);
        for (int i=0; i<counter; i++){
            this->Items->Add(textLineArray[i]);
            textLineArray_store[i] = textLineArray[i];
        }
        this->FormattingEnabled = true;
        this->Size = System::Drawing::Size(380, 225);
        this->TabIndex = 0;
        this->SelectedIndexChanged += gcnew System::EventHandler(this, &Extended_ListBox::listBox1_SelectedIndexChanged);
    }
    public Extended_ListBox(){
        this->FormattingEnabled = true;
        this->Size = System::Drawing::Size(380, 225);
        this->TabIndex = 0;
        this->SelectedIndexChanged += gcnew System::EventHandler(this, &Extended_ListBox::listBox1_SelectedIndexChanged);
    }
    private: System::Void listBox1_SelectedIndexChanged(System::Object^  sender, System::EventArgs^  e) {
                 int index=this->SelectedIndex;
                 tempstring = textLineArray_store[index];
         }  

private: array<String ^> ^ textLineArray_store;
private: String ^tempstring;
public: String ^GetSelectedString(){
            return tempstring;
        }
public: void ListBox_Update(array <String ^> ^ textLineArray, int counter){
        textLineArray_store = gcnew array<String ^>(counter);
        for (int i=0; i<counter; i++){
            this->Items->Add(textLineArray[i]);
            textLineArray_store[i] = textLineArray[i];
        }
        }
};

Answer 1

In C++/CLI, you specify the access modifier (public, private, etc.) differently than in, say, C# or Java.

Instead, you just write one line (note the colon, which is required):

public:

and all the following members are public. So insert that line before your constructors and remove the public keyword before the constructors. Like that:

public ref class Extended_ListBox: public ListBox{  
public:
    Extended_ListBox(array<String ^> ^ textLineArray, int counter){
        // constructor code
    }

    Extended_ListBox(){
        // default constructor code
    }

    // other public members 
    // ...

private:
    // private members
    // ...
}

Similar to the members below the constructors in your current example, except that you don’t have to explicitly restate public: or private: if the next member has the same visibility.