C# List querying and grouping
<p>I have this list:</p>

<pre><code>OrderId    ProductId    DateTime

1               1                10.01.2012
1               2                09.01.2012
2               1                11.01.2012
3               1                12.01.2012
3               2                13.01.2012
</code></pre>

<p>I want to extract another another List from this that's only <code>ProductId==1</code> and DateTime is <code>10.01.2012</code>.</p>

<p>i.e. only <code>productId==1</code> for every OrderId's.</p>

<p>Also I only want the least dateTime version of that item. </p>

<p>So for the above list, 10.01.2012 is the least dateTime where the productId==1.</p>

<p>Result Table;</p>

<pre><code>OrderId    ProductId    DateTime

1               1                10.01.2012
</code></pre>

<p>how can I do this?</p>
