show items value in memo

Question

C++ Builder XE8

if i select Num 1 Memo will show Test

if i select other items memo will show Else Test

void __fastcall TForm1::FormCreate(TObject *Sender)
{
    ListBox1->Items->Add("Num 1");
    ListBox1->Items->Add("Num 2");
    ListBox1->Items->Add("Num 3");

    auto str = listBox1->SelectedItem->ToString();
    if (str == L"Num 1") {
        Memo1->Text = "Test";
    }
    else {
        Memo1->Text = "Else Test";
    }
}

Answer 1

The Form's OnCreate event (which you SHOULD NOT be using in C++, use the Form's constructor instead) is too soon to detect the user's selection, as the user has not had a chance to see the UI yet to select anything. Use the ListBox's OnChange event instead.

Also, TListBox does not have a SelectedItem property. In FireMonkey (which I assume you are using instead of VCL), it has a Selected property instead.

Try this:

__fastcall TForm1::TForm1(TComponent *Owner)
    : TForm(Owner)
{
    ListBox1->BeginUpdate();
    try { 
        ListBox1->Items->Add("Num 1");
        ListBox1->Items->Add("Num 2");
        ListBox1->Items->Add("Num 3");
    }
    __finally {
        ListBox1->EndUpdate();
    }
}

void __fastcall TForm1::ListBox1Change(TObject *Sender)
{
    TListBoxItem *Item = ListBox1->Selected;
    if (Item) {
        String str = ListBox1->Selected->Text;
        if (str == L"Num 1") {
            Memo1->Text = "Test";
        }
        else {
            Memo1->Text = "Else Test";
        }
    }
    else {
        Memo1->Text = "Nothing";
    }
}