StringBuilderCharInit.qhelp

<!DOCTYPE qhelp PUBLIC
  "-//Semmle//qhelp//EN"
  "qhelp.dtd">
<qhelp>
<overview>
<p>Passing a character to the constructor of <code>StringBuilder</code> is probably intended to insert
the character into the string. In fact, however, the character value is converted to an integer and 
interpreted as the internal buffer's initial capacity, so the character value is not inserted into the string.</p>
</overview>

<example>

<p>The following example shows a <code>ToString()</code> method which formats the contents of an array.
However, the expression <code>new StringBuilder('(')</code> does not add the character <code>'('</code>
to the string <code>str</code> but merely initializes the size of the buffer, so the resulting string 
does not contain the leading <code>'('</code> character.</p>

<sample src="StringBuilderCharInit.cs" />

<p>Note that passing a character to <code>Append()</code>, on the other hand, is unproblematic.</p>

<p>The problem can be fixed by initializing the <code>StringBuilder</code>
with a string, which <em>does</em> put <code>"("</code> at the start of the string.</p>

<sample src="StringBuilderCharInitFix.cs" />

</example>
<recommendation>

<p>If the character used to initialize the buffer is a character literal, simply replace it with the
corresponding string literal. So, in our example, replace <code>new StringBuilder('(')</code> with
<code>new StringBuilder("(")</code>. If the character is not a literal value, use <code>ToString()</code>
to convert it to a string, or use an additional call to <code>Append()</code> to insert the value into
the string.</p>

</recommendation>
<references>

<li>MSDN: <a href="https://msdn.microsoft.com/en-us/library/system.text.stringbuilder.aspx">StringBuilder Class</a></li>

</references>
</qhelp>