Merge pull request #3842 from scottlocknet/fix/compatible-nullcheck

Fix incompatible null check for net standard

CHANGELOG.md

@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed a bug where path parameters deduplication would create collisions on sub path segments. [#3757](https://github.com/microsoft/kiota/issues/3757)
 - Moved from net7 to net8.
 - Removed windows OS from docker multi-partform image to align with [dotnet changes](https://github.com/dotnet/dotnet-docker/issues/4492).
+- Fixed a bug where the emitted CSharp would not be compatible with netstandad2.0. [#3829](https://github.com/microsoft/kiota/issues/3829)
 - Fixed a bug where import statements for additionalDataHolder and enumSet are missing when BackingStore is enabled in java. [#3643](https://github.com/microsoft/kiota/pull/3643)
 - Fixed an issue where Kiota's regex's might time out. [#3797](https://github.com/microsoft/kiota/issues/3797)
 - Fixed a bug where getBackingStore method body was malformed for java. [#3643](https://github.com/microsoft/kiota/pull/3643)  

src/Kiota.Builder/Writers/CSharp/CSharpConventionService.cs

@@ -96,7 +96,7 @@ internal void AddParametersAssignment(LanguageWriter writer, CodeTypeBase pathPa
                     if (nameof(String).Equals(ct.Name, StringComparison.OrdinalIgnoreCase))
                         nullCheck = $"if (!string.IsNullOrWhiteSpace({identName})) ";
                     else
-                        nullCheck = $"if ({identName} is not null) ";
+                        nullCheck = $"if ({identName} != null) ";
                 }
                 return $"{nullCheck}{varName}.Add(\"{name}\", {identName});";
             }).ToArray());