CEdit numeric validation event C++ MFC - c++

Question

I have a CEdit text box which is a part of a property pane and only allows numeric values (positive integers). The box works fine when people enter non-numeric values, but when they delete the value in the box a dialog pops up saying:
"Please enter a positive integer."
Here is the situation:
1. I have a number (say 20) in the box.
2. I delete the number.
3. I get the error dialog.
Could anybody tell me how I can intercept this event and put a default value in there?
Here is what my property pane looks like:
const int DEFAULT_VALUE = 20;
class MyPropertyPane:public CPropertyPane
{
//....
private:
CEdit m_NumericBox;
int m_value;
//....
public:
afx_msg void OnEnChangeNumericBox();
//....
}
void MyPropertyPane::MyPropertyPane()
{
// Set a default value
m_value = DEFAULT_VALUE;
}
//....
void MyPropertyPane::DoDataExchange(CDataExchange* pDX)
{
DDX_Control(pDX, IDC_NUMERIC_BOX, m_NumericBox);
// this sets the displayed value to 20
DDX_Text(pDX, IDC_NUMERIC_BOX, m_value);
}
//....
void MyPropertyPane::OnEnChangeNumericBox()
{
// Somebody deleted the value in the box and I got an event
// saying that the value is changed.
// I try to get the value from the box by updating my data
UpdateData(TRUE);
// m_value is still 20 although the value is
// deleted inside the text box.
}

Answer 1

The message you are receiving is coming from the data validation routines, not the data exchange routines. There is probably a call like this in DoDataExchange():
void MyPropertyPane::DoDataExchange(CDataExchange* pDX)
{
DDX_Control(pDX, IDC_NUMERIC_BOX, m_NumericBox);
DDX_Text(pDX, IDC_NUMERIC_BOX, m_value);
DDV_MinMaxInt(pDX, m_value, 1, 20); // if the value in m_value is outside the range 1-20, MFC will pop up an error dialog
}
You can fix this problem by removing the built-in MFC data validation and adding your own:
void MyPropertyPane::DoDataExchange(CDataExchange* pDX)
{
DDX_Control(pDX, IDC_NUMERIC_BOX, m_NumericBox);
DDX_Text(pDX, IDC_NUMERIC_BOX, m_value);
if( m_value < 1 || m_value > 20 )
{
m_value = DefaultValue;
}
}

Answer 2

John Dibling's hint led me to this solution:
void MyPropertyPane::OnEnChangeNumericBox()
{
UpdateData(TRUE);
CString value;
m_NumericBox.GetWindowText(value);
if( value.IsEmpty() )
{
m_value = DEFAULT_VALUE;
UpdateData(FALSE);
}
}
The ONLY validation that I really had to do is to check that the box contains a value, since the actual numeric validation is already handled by the box. The user can't enter a non-numeric value, but they can delete the existing one so that was a situation which was hard to handle in the data exchange function and I had to "hack" the OnChange event.

Answer 3

This one worked for me
void CtimersDlg::OnEnChangeInterval()
{
CString value; //or use char *
CWnd *pWnd = GetDlgItem(IDC_INTERVAL);//IDC_EDITBOX
if(pWnd)
{
pWnd->GetWindowTextW(value);
}
int i = _wtoi(value); //if char * use _atol()
if((!value.IsEmpty())&& (i)) //To check i = 0 or 00 entered or not
UpdateData(TRUE);
}