[csharp] Removed .net6 and .net7 (OpenAPITools#20449)

* removed .net6 and .net7

* build docs

* build docs

Author: devhl-labs

docs/generators/csharp.md

@@ -47,7 +47,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |releaseNote|Release note, default to 'Minor update'.| |Minor update|
 |returnICollection|Return ICollection<T> instead of the concrete type.| |false|
 |sourceFolder|source folder for generated code| |src|
-|targetFramework|The target .NET framework version. To target multiple frameworks, use `;` as the separator, e.g. `netstandard2.1;netcoreapp3.1`|<dl><dt>**netstandard1.3**</dt><dd>.NET Standard 1.3</dd><dt>**netstandard1.4**</dt><dd>.NET Standard 1.4</dd><dt>**netstandard1.5**</dt><dd>.NET Standard 1.5</dd><dt>**netstandard1.6**</dt><dd>.NET Standard 1.6</dd><dt>**netstandard2.0**</dt><dd>.NET Standard 2.0</dd><dt>**netstandard2.1**</dt><dd>.NET Standard 2.1</dd><dt>**net47**</dt><dd>.NET Framework 4.7</dd><dt>**net48**</dt><dd>.NET Framework 4.8</dd><dt>**net6.0**</dt><dd>.NET 6.0 (End of Support 12 November 2024)</dd><dt>**net7.0**</dt><dd>.NET 7.0</dd><dt>**net8.0**</dt><dd>.NET 8.0</dd><dt>**net9.0**</dt><dd>.NET 9.0</dd></dl>|net9.0|
+|targetFramework|The target .NET framework version. To target multiple frameworks, use `;` as the separator, e.g. `netstandard2.1;netcoreapp3.1`|<dl><dt>**netstandard1.3**</dt><dd>.NET Standard 1.3</dd><dt>**netstandard1.4**</dt><dd>.NET Standard 1.4</dd><dt>**netstandard1.5**</dt><dd>.NET Standard 1.5</dd><dt>**netstandard1.6**</dt><dd>.NET Standard 1.6</dd><dt>**netstandard2.0**</dt><dd>.NET Standard 2.0</dd><dt>**netstandard2.1**</dt><dd>.NET Standard 2.1</dd><dt>**net47**</dt><dd>.NET Framework 4.7</dd><dt>**net48**</dt><dd>.NET Framework 4.8</dd><dt>**net8.0**</dt><dd>.NET 8.0 (End of Support 10 November 2026)</dd><dt>**net9.0**</dt><dd>.NET 9.0 (End of Support 12 May 2026)</dd></dl>|net9.0|
 |useCollection|Deserialize array types to Collection&lt;T&gt; instead of List&lt;T&gt;.| |false|
 |useDateTimeForDate|Use DateTime to model date properties even if DateOnly supported. (.net 6.0+ only)| |false|
 |useDateTimeOffset|Use DateTimeOffset to model date-time properties| |false|

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpClientCodegen.java

@@ -88,8 +88,6 @@ public class CSharpClientCodegen extends AbstractCSharpCodegen {
             FrameworkStrategy.NETSTANDARD_2_1,
             FrameworkStrategy.NETFRAMEWORK_4_7,
             FrameworkStrategy.NETFRAMEWORK_4_8,
-            FrameworkStrategy.NET_6_0,
-            FrameworkStrategy.NET_7_0,
             FrameworkStrategy.NET_8_0,
             FrameworkStrategy.NET_9_0
     );
@@ -1428,13 +1426,9 @@ private static abstract class FrameworkStrategy {
         };
         static FrameworkStrategy NETFRAMEWORK_4_8 = new FrameworkStrategy("net48", ".NET Framework 4.8", "net48", Boolean.FALSE) {
         };
-        static FrameworkStrategy NET_6_0 = new FrameworkStrategy("net6.0", ".NET 6.0 (End of Support 12 November 2024)", "net6.0", Boolean.FALSE) {
+        static FrameworkStrategy NET_8_0 = new FrameworkStrategy("net8.0", ".NET 8.0 (End of Support 10 November 2026)", "net8.0", Boolean.FALSE) {
         };
-        static FrameworkStrategy NET_7_0 = new FrameworkStrategy("net7.0", ".NET 7.0", "net7.0", Boolean.FALSE) {
-        };
-        static FrameworkStrategy NET_8_0 = new FrameworkStrategy("net8.0", ".NET 8.0", "net8.0", Boolean.FALSE) {
-        };
-        static FrameworkStrategy NET_9_0 = new FrameworkStrategy("net9.0", ".NET 9.0", "net9.0", Boolean.FALSE) {
+        static FrameworkStrategy NET_9_0 = new FrameworkStrategy("net9.0", ".NET 9.0 (End of Support 12 May 2026)", "net9.0", Boolean.FALSE) {
         };
         protected String name;
         protected String description;