I am able to receive the data through serial port but I want to see it in richtextbox.

Hi,

This is an old and commonly asked question. What you are seeing is that your data from the serial port is being received on another thread. The thread that is running the Windows UI is different. It's like two different machines running in the same house, but one has no idea how to deal with the other.

So you need what's called a delegate.

See the code below.

// I've named this 'StringDelegate' - returns void and carries a string.
delegate void StringDelegate(string text); 


// Look at your rich text box, use the rich text box control's 
// name property in place where I have written 'richTextBox1'


//
// Call this method directly with the 
// data from your Serial port.
//
private void SetText(string text)  
{  
    // InvokeRequired required compares the thread ID of the  
    // calling thread to the thread ID of the creating thread.  
    // If these threads are different, it returns true.  
    if (this.richTextBox1.InvokeRequired)  
    {     

        StringArgReturningVoidDelegate d = new StringArgReturningVoidDelegate(SetText);  
        this.Invoke(d, new object[] { text });  
    }  
    else  
    {  
        this.richTextBox1.Text = text;  
    }  
}