<p>Lets say you have a:</p>

<pre><code>List&lt;string&gt; los = new List&lt;string&gt;();
</code></pre>

<p>In this crazy functional world we live in these days which one of these would be best for creating one string by concatenating these:</p>

<pre><code>String.Join(String.Empty, los.ToArray());

StringBuilder builder = new StringBuilder();
los.ForEach(s =&gt; builder.Append(s));

string disp = los.Aggregate&lt;string&gt;((a, b) =&gt; a + b);
</code></pre>

<p>or Plain old StringBuilder foreach</p>

<p>OR is there a better way?</p>

I would go with option A:
```
```
String.Join(String.Empty, los.ToArray());
```
```
My reasoning is because the Join method was written for that purpose. In fact if you look at Reflector, you'll see that unsafe code was used to really optimize it. The other two also WORK, but I think the Join function was written for this purpose, and I would guess, the most efficient. I could be wrong though...
As per @Nuri YILMAZ without
```
.ToArray()
```
, but this is .NET 4+:
```
```
String.Join(String.Empty, los);
```
```