In .NET 2.0 it uses the String
class internally. String
is only immutable outside of the System
namespace, so StringBuilder
can do that.
In .NET 4.0 String
was changed to use char[]
.
In 2.0 StringBuilder
looked like this
public sealed class StringBuilder : ISerializable
{
// Fields
private const string CapacityField = "Capacity";
internal const int DefaultCapacity = 0x10;
internal IntPtr m_currentThread;
internal int m_MaxCapacity;
internal volatile string m_StringValue; // HERE ----------------------
private const string MaxCapacityField = "m_MaxCapacity";
private const string StringValueField = "m_StringValue";
private const string ThreadIDField = "m_currentThread";
But in 4.0 it looks like this:
public sealed class StringBuilder : ISerializable
{
// Fields
private const string CapacityField = "Capacity";
internal const int DefaultCapacity = 0x10;
internal char[] m_ChunkChars; // HERE --------------------------------
internal int m_ChunkLength;
internal int m_ChunkOffset;
internal StringBuilder m_ChunkPrevious;
internal int m_MaxCapacity;
private const string MaxCapacityField = "m_MaxCapacity";
internal const int MaxChunkSize = 0x1f40;
private const string StringValueField = "m_StringValue";
private const string ThreadIDField = "m_currentThread";
So evidently it was changed from using a string
to using a char[]
.
EDIT: Updated answer to reflect changes in .NET 4 (that I only just discovered).
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