printing data in text box in serial communication using timer

[tharunsigma]

iam new to c# and trying to work out on serial communication using timer i can send and receive the data but during printing of the received data the incoming data is overlapped on the previous data..
Please help me in advancing....and my code is as follows...`

        int nDataLen = newSerialport.ReadBufferSize;
        int nLeng = newSerialport.BytesToRead;
        if (nLeng != 0)
        {
            newSerialport.Read(chRead, 0, 20);
            for(int i=0;i<20;i++)
            stRecvData = System.Text.Encoding.UTF8.GetString(chRead);
            //textBox_Recv.Text = stRecvData;
        }               
        else
        {
            ;
        }
        textBox_Recv.Text = stRecvData;`