C# Regex - String contains at least one dot and any number of blanks
<p>I'm looking for a Regex to test if a String only contains at least one dot "." and random number of blanks " ".</p>

<p>Strings that should match:</p>

<ul>
<li>"." </li>
<li>". ."</li>
<li>" ..."</li>
<li>". .. . "</li>
<li>"......"</li>
</ul>

<p>and so on</p>

<p>Thank you for your help!</p>