How do I create a message box with "Yes", "No" choices and a DialogResult?

MessageBox.Show(title, text, messageboxbuttons.yes/no)

This returns a DialogResult which you can check.

For example,

if(MessageBox.Show("","",MessageBoxButtons.YesNo) == DialogResult.Yes)
{
   //do something
}

The MessageBox does produce a DialogResults

DialogResult r = MessageBox.Show("Some question here");

You can also specify the buttons easily enough. More documentation can be found at http://msdn.microsoft.com/en-us/library/ba2a6d06.aspx

DialogResult dr = MessageBox.Show("Are you happy now?", 
                      "Mood Test", MessageBoxButtons.YesNo);
switch(dr)
{
   case DialogResult.Yes:
      break;
   case DialogResult.No:
      break;
}

MessageBox class is what you are looking for.

This should do it:

DialogResult dialogResult = MessageBox.Show("Sure", "Some Title", MessageBoxButtons.YesNo);
if(dialogResult == DialogResult.Yes)
{
    //do something
}
else if (dialogResult == DialogResult.No)
{
    //do something else
}