# Improvements to C# analysis

> NOTES
>
> Please describe your changes in terms that are suitable for
> customers to read. These notes will have only minor tidying up
> before they are published as part of the release notes.

## General improvements

> Changes that affect alerts in many files or from many queries
> For example, changes to file classification

## New queries

| **Query**                   | **Tags**  | **Purpose**                                                        |
|-----------------------------|-----------|--------------------------------------------------------------------|
| Constant condition (cs/constant-condition) | More results | The query has been generalized to cover both `Null-coalescing left operand is constant (cs/constant-null-coalescing)` and `Switch selector is constant (cs/constant-switch-selector)`. |
| Exposing internal representation (cs/expose-implementation) | Different results | The query has been rewritten, based on the equivalent Java query. |
| Local scope variable shadows member (cs/local-shadows-member) | maintainability, readability | Replaces the existing queries [Local variable shadows class member (cs/local-shadows-class-member)](https://help.semmle.com/wiki/display/CSHARP/Local+variable+shadows+class+member), [Local variable shadows struct member (cs/local-shadows-struct-member)](https://help.semmle.com/wiki/display/CSHARP/Local+variable+shadows+struct+member), [Parameter shadows class member (cs/parameter-shadows-class-member)](https://help.semmle.com/wiki/display/CSHARP/Parameter+shadows+class+member), and [Parameter shadows struct member (cs/parameter-shadows-struct-member)](https://help.semmle.com/wiki/display/CSHARP/Parameter+shadows+struct+member). |
| Null-coalescing left operand is constant (cs/constant-null-coalescing) | No results | The query has been removed, as it is now covered by `Constant condition (cs/constant-condition)`. |
| Switch selector is constant (cs/constant-switch-selector) | No results | The query has been removed, as it is now covered by `Constant condition (cs/constant-condition)`. |

## Changes to existing queries

| **Query**                  | **Expected impact**    | **Change**                                                       |
|----------------------------|------------------------|------------------------------------------------------------------|
| [Missing Dispose call on local IDisposable (cs/local-not-disposed)](https://help.semmle.com/wiki/display/CSHARP/Missing+Dispose+call+on+local+IDisposable) | Fewer results | The query identifies more cases where the local variable may be disposed by a library call. |
| [Nested loops with same variable (cs/nested-loops-with-same-variable)](https://help.semmle.com/wiki/display/CSHARP/Nested+loops+with+same+variable) | Fewer results | Results are no longer highlighted in nested loops that share the same condition, and do not use the variable after the inner loop. |
| [Potentially incorrect CompareTo(...) signature (cs/wrong-compareto-signature)](https://help.semmle.com/wiki/display/CSHARP/Potentially+incorrect+CompareTo%28...%29+signature) | Fewer results | Results are no longer highlighted in constructed types. |
| [Useless upcast (cs/useless-upcast)](https://help.semmle.com/wiki/display/CSHARP/Useless+upcast) | Fewer results | The query has been improved to cover more cases where upcasts may be needed. |

## Changes to code extraction

* *Series of bullet points*

## Changes to QL libraries

* A new non-member predicate `mayBeDisposed()` can be used to determine if a variable is potentially disposed inside a library. It will analyse the CIL code in the library to determine this.