MessageBox.Show("your message",
    "window title", 
    MessageBoxButtons.OK, 
    MessageBoxIcon.Warning // for Warning  
    //MessageBoxIcon.Error // for Error 
    //MessageBoxIcon.Information  // for Information
    //MessageBoxIcon.Question // for Question
   );

//MessageBox.Result
DialogResult result = MessageBox.Show("Do you like cats?", "Yes or No?", messageBoxButtons.YesNoCancel);

if (result == DialogResult.Yes)
    ;
else if (result == DialogResult.No)
    ;
else
    ;