Dotnet: Fix warnings

Author: Denis-Averin

codegen/Templates/csharp/Project.mustache

@@ -3,6 +3,7 @@
   <PropertyGroup>
     <TargetFrameworks>netstandard2.0</TargetFrameworks>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+    <WarningsNotAsErrors>IDE0005;IDE0008;IDE1006</WarningsNotAsErrors>
     <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
     <AnalysisLevel>latest-Recommended</AnalysisLevel>
 

codegen/Templates/csharp/api.mustache

@@ -128,12 +128,8 @@ namespace {{packageName}}.Api
                 null,
                 {{#hasFormParams}}formParams{{/hasFormParams}}{{^hasFormParams}}null{{/hasFormParams}});
 
-            if (response != null)
-            {
-                return ({{returnType}}) SerializationHelper.Deserialize(response, typeof({{returnType}}));
-            }
+            return response == null ? null : ({{returnType}}) SerializationHelper.Deserialize(response, typeof({{returnType}}));
 
-            return null;
             {{/returnType}}
             {{^returnType}}
             await _apiInvoker.InvokeApiAsync(