I have this RTF text:
{\\rtf1\\ansi\\ansicpg1252\\deff0\\deflang1033{\\fonttbl{\\f0\\fnil\\fcharset0 Arial;}} {\\colortbl ;\\red0\\green0\\blue0;\\red255\\green0\
string rtf = @"{\rtf1\ansi\ansicpg1252\deff0\deflang1033{\fonttbl{\f0\fnil\fcharset0 Arial;}} {\colortbl ;\red0\green0\blue0;\red255\green0\blue0;} \viewkind4\uc1\pard\qc\cf1\fs16 test \b bold \cf2\b0\i italic\cf0\i0\fs17 \par } "; richTextBox1.Rtf = rtf;
It's working fine