Update C# docs (#49789)

Release Notes:

- N/A

docs/src/languages/csharp.md

@@ -5,16 +5,116 @@ description: "Configure C# language support in Zed, including language servers,
 
 # C#
 
-Note language name is "CSharp" for settings not "C#'
-
 C# support is available through the [C# extension](https://github.com/zed-extensions/csharp).
 
 - Tree-sitter: [tree-sitter/tree-sitter-c-sharp](https://github.com/tree-sitter/tree-sitter-c-sharp)
-- Language Server: [OmniSharp/omnisharp-roslyn](https://github.com/OmniSharp/omnisharp-roslyn)
+- Language Servers:
+  - [roslyn-language-server](https://www.nuget.org/packages/roslyn-language-server#readme)
+  - [OmniSharp/omnisharp-roslyn](https://github.com/OmniSharp/omnisharp-roslyn)
+
+Roslyn is enabled by default. To switch back to OmniSharp, add the following to your Zed settings file:
+
+```json [settings]
+{
+  "languages": {
+    "CSharp": {
+      "language_servers": ["omnisharp", "!roslyn", "..."]
+    }
+  }
+}
+```
+
+Note: the language name used in settings is "CSharp", not "C#".
 
 ## Configuration
 
-The `OmniSharp` binary can be configured in a Zed settings file with:
+Roslyn can be configured with the following language server settings:
+
+```json [settings]
+{
+  "lsp": {
+    "roslyn": {
+      "settings": {
+        // Default values are shown below, along with alternative options where applicable.
+        "csharp|symbol_search": {
+          "dotnet_search_reference_assemblies": true
+        },
+        "csharp|type_members": {
+          "dotnet_member_insertion_location": "atTheEnd", // or "withOtherMembersOfTheSameKind"
+          "dotnet_property_generation_behavior": "preferThrowingProperties" // or "preferAutoProperties"
+        },
+        "csharp|completion": {
+          "dotnet_show_name_completion_suggestions": true,
+          "dotnet_provide_regex_completions": true,
+          "dotnet_show_completion_items_from_unimported_namespaces": true,
+          "dotnet_trigger_completion_in_argument_lists": true
+        },
+        "csharp|quick_info": {
+          "dotnet_show_remarks_in_quick_info": true
+        },
+        "csharp|navigation": {
+          "dotnet_navigate_to_decompiled_sources": true,
+          "dotnet_navigate_to_source_link_and_embedded_sources": true
+        },
+        "csharp|highlighting": {
+          "dotnet_highlight_related_json_components": true,
+          "dotnet_highlight_related_regex_components": true
+        },
+        "csharp|inlay_hints": {
+          "dotnet_enable_inlay_hints_for_parameters": true,
+          "dotnet_enable_inlay_hints_for_literal_parameters": true,
+          "dotnet_enable_inlay_hints_for_indexer_parameters": true,
+          "dotnet_enable_inlay_hints_for_object_creation_parameters": true,
+          "dotnet_enable_inlay_hints_for_other_parameters": true,
+          "dotnet_suppress_inlay_hints_for_parameters_that_differ_only_by_suffix": true,
+          "dotnet_suppress_inlay_hints_for_parameters_that_match_method_intent": true,
+          "dotnet_suppress_inlay_hints_for_parameters_that_match_argument_name": true,
+          "csharp_enable_inlay_hints_for_types": true,
+          "csharp_enable_inlay_hints_for_implicit_variable_types": true,
+          "csharp_enable_inlay_hints_for_lambda_parameter_types": true,
+          "csharp_enable_inlay_hints_for_implicit_object_creation": true,
+          "csharp_enable_inlay_hints_for_collection_expressions": true
+        },
+        "csharp|code_style.formatting.indentation_and_spacing": {
+          "tab_width": 4,
+          "indent_size": 4,
+          "indent_style": "space" // or "tab"
+        },
+        "csharp|code_style.formatting.new_line": {
+          "end_of_line": "...", // platform-specific default
+          "insert_final_newline": false
+        },
+        "csharp|background_analysis": {
+          "dotnet_analyzer_diagnostics_scope": "default", // or "none" "openFiles" "fullSolution"
+          "dotnet_compiler_diagnostics_scope": "openFiles" // or "fullSolution"
+        },
+        "csharp|code_lens": {
+          "dotnet_enable_references_code_lens": false,
+          "dotnet_enable_tests_code_lens": false
+        },
+        "csharp|auto_insert": {
+          "dotnet_enable_auto_insert": true
+        },
+        "csharp|projects": {
+          "dotnet_binary_log_path": null,
+          "dotnet_enable_automatic_restore": true,
+          "dotnet_enable_file_based_programs": true,
+          "dotnet_enable_file_based_programs_when_ambiguous": true
+        },
+        "csharp|formatting": {
+          "dotnet_organize_imports_on_format": false
+        }
+      },
+      "binary": {
+        "path": "/path/to/roslyn-language-server",
+        "arguments": ["--stdio", "--autoLoadProjects" /* add extra arguments */]
+      }
+    }
+  }
+}
+```
+
+OmniSharp can be configured in a Zed settings file with:
 
 ```json [settings]
 {
@@ -22,7 +122,7 @@ The `OmniSharp` binary can be configured in a Zed settings file with:
     "omnisharp": {
       "binary": {
         "path": "/path/to/OmniSharp",
-        "arguments": ["optional", "additional", "args", "-lsp"]
+        "arguments": ["-lsp" /* add extra arguments */]
       }
     }
   }