File Regex with extension c# : <p>I want to check the name of the file. it supposed to accept only letters with an extension of .xlsm </p>

<p>I tried this: </p>

<blockquote>
  <p>^[a-zA-Z]+$.xlsm</p>
</blockquote>

<p>can anybody please explain a little bit about this regex if it is correct. 
what the ^, +, $ means? and should I add something? </p>

<p>thank you</p>
