StringBuilder.Length property is not readonly
For your information, the StringBuilder's Length property is not readonly just like the String class. It has a mutator (set counterpart) where you can set the underlying string's length which can either truncate the underlying string or pad it with spaces. You don't have to use
myStringBuilder.Remove(0, myStringBuilder.Length)
just to reuse your stringbuilder instance, just set its Length property to 0.
myStringBuilder.Length = 0