Period in wrong place:
"...provided with the. NET Framework."
should be
"...provided with the .NET Framework."

Double "not only" in "...not only provide not only a comprehensive overview..."

Missing apostrophe in
"Security is a known requirement of the systems users."
It should be
"Security is a known requirement of the system's users."

Should be "created" instead of "creating" in
"...SumNumbers.netmodule is creating from a C# class..."
it should say:
"...SumNumbers.netmodule is created from a C# class..."

Incorrect use of "it's". Should be "its" in
"...leaving development of it's components to individual development teams."

"In this regard, your unit testing is a simplified form of the security testing that we proscribe below."
it should be:
"In this regard, your unit testing is a simplified form of the security testing that we prescribe below."
It should be "prescribe" not "proscribe"

It should be "is focused" instead of "are focused" and "is progressing" instead of
"is in progressing" in "The first generation of tools are focused on testing the
...configuration of an application and the .NET runtime, but work is in progressing on more complex software that ...
should be:
...configuration of an application and the .NET runtime, but work is progressing on more complex software that ...

In contrast, because the FilIOPermission class ...
This should be
In contrast, because the FileIOPermission class ...

Change StringName to StrongName under Evidence type represented

"SecurtityPermisson" in the first sentence is spelled incorrectly.
It should be: "SecurityPermission"

Description for ComputeHash has incorrect cross-reference.
It should read:
See the "Hashing Data from Memory" and "Hashing Streamed Data" sections in this chapter for full details.

The .NET Framework exposes ELS functionality through the System.Diagnotics.EventLog class;
should be:
The .NET Framework exposes ELS functionality through the System.Diagnostics.EventLog class;