Report Viewer Winform control cannot display HTML placeholder correctly by EricCS07

I use a Report Viewer winform control (Microsoft.ReportViewer.WinForms.dll 9.0.30729.4402) in my application to display a report with textboxes showing HTML placeholder contents as below. However, the characters are all showing as plain text. This does not occur on WebForm control of same version and Winform control on VS2010.

textbox 1:

="<P>this is a test 1</P><P><U><FONT size=5>this is a test 2</FONT></U></P><P><EM><FONT color=#c00000><STRONG>this is a test 3</STRONG></FONT></EM></P><P> </P><P> </P>"

textbox 2:
="<P>this is a test 1</P><P><U>this is a test 2</U></P>"

textbox3:
="<P>this is a test 1</P><P><B>this is a test 2</B></P>"