[CS] Verifier (#7850)

* Fix C/C++ Create<Type>Direct with sorted vectors

If a struct has a key the vector has to be sorted. To sort the vector
you can't use "const".

* Changes due to code review

* Improve code readability

* Add generate of JSON schema to string to lib

* option indent_step is supported

* Remove unused variables

* Fix break in test

* Fix style to be consistent with rest of the code

* [TS] Fix reserved words as arguments (#6955)

* [TS] Fix generation of reserved words in object api (#7106)

* [TS] Fix generation of object api

* [TS] Fix MakeCamel -> ConvertCase

* [C#] Fix collision of field name and type name

* [TS] Add test for struct of struct of struct

* Update generated files

* Add missing files

* [TS] Fix query of null/undefined fields in object api

* Add .Net verfier

* Add some fuzz tests for .Net

* Remove additional files

* Fix .net test

* Changes due to PR

* Fix generated files

---------

Co-authored-by: Derek Bailey <derekbailey@google.com>

docs/source/CsharpUsage.md

@@ -142,6 +142,47 @@ To use it:
     `ByKey` only works if the vector has been sorted, it will
     likely not find elements if it hasn't been sorted.
 
+## Buffer verification 
+
+As mentioned in [C++ Usage](@ref flatbuffers_guide_use_cpp) buffer
+accessor functions do not verify buffer offsets at run-time. 
+If it is necessary, you can optionally use a buffer verifier before you
+access the data. This verifier will check all offsets, all sizes of
+fields, and null termination of strings to ensure that when a buffer
+is accessed, all reads will end up inside the buffer.
+
+Each root type will have a verification function generated for it,
+e.g. `Monster.VerifyMonster`. This can be called as shown:
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cs}
+    var ok = Monster.VerifyMonster(buf);
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+if `ok` is true, the buffer is safe to read.
+
+For a more detailed control of verification `MonsterVerify.Verify` 
+for `Monster` type can be used: 
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cs}
+    # Sequence of calls
+    FlatBuffers.Verifier verifier = new FlatBuffers.Verifier(buf);
+    var ok = verifier.VerifyBuffer("MONS", false, MonsterVerify.Verify);
+    
+    # Or single line call 
+    var ok = new FlatBuffers.Verifier(bb).setStringCheck(true).\
+             VerifyBuffer("MONS", false, MonsterVerify.Verify);
+       
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+if `ok` is true, the buffer is safe to read.
+
+A second parameter of `verifyBuffer` specifies whether buffer content is
+size prefixed or not. In the example above, the buffer is assumed to not include
+size prefix (`false`).
+
+Verifier supports options that can be set using appropriate fluent methods:
+* SetMaxDepth - limit the nesting depth. Default: 1000000
+* SetMaxTables - total amount of tables the verifier may encounter. Default: 64
+* SetAlignmentCheck - check content alignment. Default: True
+* SetStringCheck - check if strings contain termination '0' character. Default: true
+
+
 ## Text parsing
 
 There currently is no support for parsing text (Schema's and JSON) directly

docs/source/doxyfile

@@ -779,7 +779,8 @@ INPUT = "FlatBuffers.md" \
         "../../python/flatbuffers/builder.py" \
         "../../js/flatbuffers.js" \
         "../../php/FlatbufferBuilder.php" \
-        "../../net/FlatBuffers/FlatBufferBuilder.cs" \
+        "../../net/FlatBuffers/FlatBufferBuilder.cs"
+        "../../net/FlatBuffers/FlatBufferVerify.cs" \
         "../../include/flatbuffers/flatbuffers.h" \
         "../../go/builder.go" \
         "../../rust/flatbuffers/src/builder.rs"