C / C++ / MFC

m_button.EnableWindow(m_edit.GetWindowTextLength() > 0);

CString name ;
m_editMineName.GetWindowText(name) ;
GetDlgItem(IDC_BUTTON_DONE)->EnableWindow(name.GetLength() > 0) ;

<br />
class CEditControlDlg : public CDialog<br />
{<br />
// Construction<br />
public:<br />
 CEdit *m_pEdit; // Added by Sayan<br />
 CButton *m_pButton; // Added by Sayan<br />
<br />
 CEditControlDlg(CWnd* pParent = NULL);	// standard constructor<br />
// ...<br />
// ...<br />
}<br />

<br />
BOOL CEditControlDlg::OnInitDialog()<br />
{<br />
 CDialog::OnInitDialog();<br />
<br />
 // Set the icon for this dialog.  The framework does this automatically<br />
 //  when the application's main window is not a dialog<br />
 SetIcon(m_hIcon, TRUE);			// Set big icon<br />
 SetIcon(m_hIcon, FALSE);		// Set small icon<br />
	<br />
 // TODO: Add extra initialization here<br />
 m_pEdit = (CEdit *)GetDlgItem(EF_TEXT); // Added by Sayan<br />
 m_pButton = (CButton *)GetDlgItem(PB_DONE); // Added by Sayan<br />
<br />
 m_pButton->EnableWindow(FALSE); // Added by Sayan<br />
 return TRUE;  // return TRUE  unless you set the focus to a control<br />
}<br />

<br />
void CEditControlDlg::OnChangeText() <br />
{<br />
 // TODO: If this is a RICHEDIT control, the control will not<br />
 // send this notification unless you override the CDialog::OnInitDialog()<br />
 // function and call CRichEditCtrl().SetEventMask()<br />
 // with the ENM_CHANGE flag ORed into the mask.<br />
	<br />
 // TODO: Add your control notification handler code here<br />
 CString strText;<br />
<br />
 m_pEdit->GetWindowText(strText);<br />
<br />
 if (!strText.GetLength())<br />
 {<br />
 	m_pButton->EnableWindow(FALSE);<br />
 }<br />
 else<br />
 {<br />
 	m_pButton->EnableWindow();<br />
 }<br />
}<br />