<p>What is the default capacity of a <code>StringBuilder</code>?</p>

<p>And when should (or shouldn't) the default be used?</p>

[edit: at the time, the question asked about
```
StringList
```
]
Do you mean
```
StringCollection
```
? This uses an empty
```
ArrayList
```
initially, so the answer is 0. And you have no option to change it. When you first add an item, the capacity jumps to 4, then uses a doubling strategy when it fills.
If you mean
```
List<string>
```
, then it is similar (an empty
```
T[]
```
, not an
```
ArrayList
```
), but you can initialize a known size if you need (i.e. you know how much data you expect). Again, the first time you
```
Add
```
to a
```
List<T>
```
the size jumps to 4, then doubles every time it fills up.