c++builder - How to put TEdit data into String C++ Builder

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I am new in programming. Actually I am in 2nd year of college and starting an internship. They want me to do a program in C++ builder but I only know C. What I studied. And I don't have any knowledge about OOP.

So my question is.

I have TEdit1 and I want to verify if the data introduced in that textbox is a number. I know to verify if it is a number but I don't know how to put data from TEdit into string.

I wrote some code but it doesn't work.

void __fastcall TForm1::Button1Click(TObject *Sender) 
    int Size = Edit1->GetTextLen(); //Get length of string in Edit1
    Size++;                         //Add room for null character
    Char *Buffer = new Char[Size];  //Creates Buffer dynamic variable
    std::auto_ptr<Char> Buffer(new Char[Size]);
    Edit1->GetTextBuf(Buffer.get(),Size); //Puts Edit1->Text into Buffer
    ShowMessage(Buffer);
And I get these errors:
 E2034 Cannot convert 'std::auto_ptr<wchar_t>' to 'UnicodeString'
 E2342 Type mismatch in parameter 'Msg' (wanted 'const UnicodeString', got              std::auto_ptr<wchar_t>')
Can you please explain what i did wrong, or where i can found Embarcadero C++ Builder tutorials? I searched all google and didn't find something to help me.
you are declaring two Buffer variables in the same scope.  That is not allowed.  You need to remove one of them.
you are passing the std::auto_ptr itself to ShowMessage(), but it expects a System::UnicodeString instead, thus the compiler error message.  You can use the std::auto_ptr::get() method to get the wchar_t* pointer and pass it to ShowMessage(), as UnicodeString has a constructor that accepts wchar_t* as input:
ShowMessage(Buffer.get());
despite the above, you actually cannot use a pointer from new[] with std::auto_ptr to begin with.  std::auto_ptr uses delete instead of delete[] to free the memory being pointed at.  You must always use delete with new, and delete[] with new[].  So, while the code will compile, it will not free the memory correctly at runtime.  C++11 introduced a new std::unique_ptr class to replace std::auto_ptr, and std::unique_ptr supports new[] and delete[] (however, C++Builder's 32bit compiler does not support C++11 yet - that is in the works - but its 64bit compiler does):
#include <memory>
void __fastcall TForm1::Button1Click(TObject *Sender) 
    int Size = Edit1->GetTextLen(); //Get length of string in Edit1
    Size++;                         //Add room for null character
    std::unique_ptr<Char[]> Buffer(new Char[Size]); //Creates Buffer dynamic variable
    Edit1->GetTextBuf(Buffer.get(), Size); //Puts Edit1->Text into Buffer
    ShowMessage(Buffer.get());
Now, with that said, if you are going to continue using C++Builder, you should learn how to use its built-in functionalities, like UnicodeString, which the RTL/VCL relies heavily on (use the System::String alias for most code, use UnicodeString directly only when absolutely necessary).
Your example can be vastly simplified using the TEdit::Text property:
void __fastcall TForm1::Button1Click(TObject *Sender) 
    String s = Edit1->Text; //Get string in Edit1
    ShowMessage(s);
The simplest solution to your problem would be to use the TCSpinEdit component instead of TEdit, as TCSpinEdit only allows numeric input in the first place, and has a Value property that returns an int:
void __fastcall TForm1::Button1Click(TObject *Sender) 
    int number = CSpinEdit1->Value;
    ShowMessage("It is a number");
    // use number as needed...
But, if you have to stick with TEdit, there are many ways to check a UnicodeString for numeric content. 
You can set the TEdit::NumbersOnly property to true so the user cannot enter a non-numeric value (unless they use copy/paste, but let's ignore that for the moment), and then use the RTL's StrToInt() function, or System::UnicodeString::ToInt() method, to convert it as-is:
#include <System.SysUtils.hpp>
void __fastcall TForm1::Button1Click(TObject *Sender) 
    int number;
        number = StrToInt(Edit1->Text);
        // or: number = Edit1->Text.ToInt();
    catch (const EConvertError&)
        // not a number, do something else...
        ShowMessage("It is not a number");
        return;
    ShowMessage("It is a number");
    // use number as needed...
Or you can use the RTL's System::Sysutils::TryStrToInt() function:
#include <System.SysUtils.hpp>
void __fastcall TForm1::Button1Click(TObject *Sender) 
    int number;
    if (TryStrToInt(Edit1->Text, number))
        // use number as needed...
        ShowMessage("It is a number");
        // not a number, do something else...
        ShowMessage("It is not a number");
Or you can use the STL's std::wistringstream class:
#include <sstream>
void __fastcall TForm1::Button1Click(TObject *Sender) 
    int number;
    std::wistringstream iss(Edit1->Text.c_str());
    if (iss >> number)
        // use number as needed...
        ShowMessage("It is a number");
        // not a number, do something else...
        ShowMessage("It is not a number");
Or, since you have a C background, you can use the C _wtoi() function (which doesn't offer much in the way of error checking):
#include <cstdlib>
void __fastcall TForm1::Button1Click(TObject *Sender) 
    int number = std::_wtoi(Edit1->Text.c_str());
    if (number != 0)
        // use number as needed...
        ShowMessage("It is a valid number");
        // not a number, do something else...
        ShowMessage("It is not a valid number");
Or you can use the C wcstol() function:
#include <cstdlib>
void __fastcall TForm1::Button1Click(TObject *Sender) 
    String s = Edit1->Text;
    Char *p = s.c_str(), *end;
    int number = std::wcstol(p, &end, 10);
    if (end != p)
        // use number as needed...
        ShowMessage("It is a number");
        // not a number, do something else...
        ShowMessage("It is not a number");
Or you can use the C swscanf() function:
#include <cstdio>
void __fastcall TForm1::Button1Click(TObject *Sender) 
    int number;
    if (std::swscanf(Edit1->Text.c_str(), L"%d", &number) == 1)
        // use number as needed...
        ShowMessage("It is a number");
        // not a number, do something else...
        ShowMessage("It is not a number");
                XE5's bcc32 has std::unique_ptr. It's not quite compliant (it requires its template parameter to be a complete type in some situations where C++11 allows an incomplete type) but it's good enough for many uses, including pImpls
– M.M
                Jul 18, 2015 at 2:54
                @MattMcNabb: sure, that would address the specific example Cantor gave, but not the overall task Cantor is trying to solve.
– Remy Lebeau
                Jul 19, 2015 at 3:33
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