How can I clear drawings done by cclientdc?

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C++

MFC

drawing

VC++

Hello people,
i am doing drawings on dialof in MFC vc++.

i am drawing lines as per the different inputs i am getting from the serial.

now i want to clear the drawings when i get another input.

What I have tried:

CClientDC dc(GetDlgItem(IDC_STATICDISPLAY));

CPen lDot(PS_DASH, 2, RGB(255, 255, 255));

dc.SelectObject(&lDot);
	dc.Rectangle(a,b,c,d);

Here a,b,c,d are my different inputs which i am getting from the serial communication.
at each input i want to clear the older drawings and draw a new lines with new data.

And

GetDlgItem(IDC_STATICDISPLAY)

is the group box in which i am drawing lines in dialog.