SaveFileDialog sfd=new SaveFileDialog();
sfd.Filter="Text file(*.txt)|*.txt|All files(*.*)|*.*";
sfd.FilterIndex=1;
sfd.RestoreDirectory=true;
StreamWriter sw=null;
if(sfd.ShowDialog()==DialogResult.OK)
{
try
{
sw=new StreamWriter (sfd.FileName,false,System.Text.Encoding.Unicode);
sw.Write(richTextBox1.Text);

}
catch(Exception ee)
{
MessageBox.Show(ee.Message,"出错",MessageBoxButtons.OK,MessageBoxIcon.Error);
}
finally
{
if(sw!=null)
{
sw.Close();
}
}
}