best way to clear contents of .NET's StringBuilder

If you're doing this in .NET 2.0 or 3.5, write an extension method to do it like this:

/// <summary>
///     Clears the contents of the string builder.
/// </summary>
/// <param name="value">
///     The <see cref="StringBuilder"/> to clear.
/// </param>
public static void Clear(this StringBuilder value)
{
    value.Length = 0;
    value.Capacity = 0;
}

Then, you can clear it like this:

someStringBuilder.Clear();

Then, when 4.0 comes out, you can ditch your extension method in favor of the 4.0 version.

UPDATE: It's probably not a good idea to set Capacity to zero. That will guarantee reallocations when you append to the builder, if you're reusing the same instance. However, the memory in the instance of the builder is not released until you set the Capacity to a very small value (such as 1). The default value of the Capacity property is 16. You might want to consider using 16, or (though it's less efficient) setting the capacity twice:

• Set it to 1 or zero to clear the memory
• Set it to your original Capacity value (which may differ from 16) to restore it.

In .NET 4.0 you can call sb.Clear() but in older versions you should set sb.Length = 0.

The Clear() method was added in .NET 4.0.

Create the new StringBuilder. The old one maintains resources associated with it (buffer of maximum length, for example) that are best just garbage collected away.