Added an example for C#

README.md

@@ -660,7 +660,6 @@ Hello LUA!
 The following example was contributed by [@r9y9](https://github.com/r9y9). It shows how to invoke exported Go functions from the Julia language. As [documented here](https://docs.julialang.org/en/stable/manual/calling-c-and-fortran-code/), Julia has the capabilities to invoke exported functions from shared libraries similar to other languages discussed here.
 
 File [client.jl](./client.jl)
-
 ```julia
 struct GoSlice
     arr::Ptr{Void}
@@ -703,7 +702,6 @@ Hello from Julia!
 The following example was contributed by @dpurfield. It shows how to invoke exported Go functions from the Dart language. As documented [here](https://dart.dev/guides/libraries/c-interop), Dart has the capability to invoke exported functions from shared libraries similar to other languages discussed here.
 
 File [client.dart](./client.dart)
-
 ```dart
 import 'dart:convert';
 import 'dart:ffi';
@@ -815,6 +813,84 @@ void main(List<String> args) {
   stdin.readByteSync();
 }
 ```
+## From C#
+To call the exported Go functions from C# we use the [DllImportAttribute](https://docs.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.dllimportattribute?view=netframework-4.8) attribute to dynamically load and call exported Go functions in the awesome.so shared object file as shown in the following snippet.
+
+File [client.cs](./client.cs)
+```cs
+using System;
+using System.Runtime.InteropServices;
+
+class Awesome
+{
+    const string libName = "awesome.so";
+
+    public struct GoSlice
+    {
+        public IntPtr data;
+        public long len, cap;
+        public GoSlice(IntPtr data, long len, long cap)
+        {
+            this.data = data;
+            this.len = len;
+            this.cap = cap;
+        }
+    }
+    public struct GoString
+    {
+        public string msg;
+        public long len;
+        public GoString(string msg, long len)
+        {
+            this.msg = msg;
+            this.len = len;
+        }
+    }
+
+    // Use DllImport to import the Awesome lib.
+    [DllImport(libName)]
+    public static extern int Add(long a, long b);
+
+    [DllImport(libName)]
+    public static extern double Cosine(double a);
+
+    [DllImport(libName)]
+    public static extern void Sort(GoSlice a);
+
+    [DllImport(libName, CharSet = CharSet.Unicode)]
+    public static extern void Log(GoString msg);
+
+    static void Main()
+    {
+        long add = Add(12, 99);
+        double cosine = Cosine(1);
+
+        long[] data = { 77, 12, 5, 99, 28, 23 };
+        IntPtr data_ptr = Marshal.AllocHGlobal(Buffer.ByteLength(data));
+        Marshal.Copy(data, 0, data_ptr, data.Length);
+        var nums = new GoSlice(data_ptr, data.Length, data.Length);
+        Sort(nums);
+        Marshal.Copy(nums.data, data, 0, data.Length);
+
+        string msg = "Hello from C#!";
+        GoString str = new GoString(msg, msg.Length);
+
+        Console.WriteLine("awesome.Add(12,99) = " + add);
+        Console.WriteLine("awesome.Cosine(1) = " + cosine);
+        Console.WriteLine("awesome.Sort(77,12,5,99,28,23): " + string.Join(", ", data));
+        Log(str);
+    }
+}
+```
+When the example is executed, it produces the following:
+
+```
+> dotnet run
+awesome.Add(12,99) = 111
+awesome.Cosine(1) = 0,5403023058681398
+awesome.Sort(77,12,5,99,28,23): 5, 12, 23, 28, 77, 99
+Hello from C#!
+```
 
 ## Conclusion
 This repo shows how to create a Go library that can be used from C, Python, Ruby, Node, Java, Lua, Julia. By compiling Go packages into C-style shared libraries, Go programmers have a powerful way of integrating their code with any modern language that supports dynamic loading and linking of shared object files.

client.cs

@@ -0,0 +1,63 @@
+using System;
+using System.Runtime.InteropServices;
+
+class Awesome
+{
+    const string libName = "awesome.so";
+
+    public struct GoSlice
+    {
+        public IntPtr data;
+        public long len, cap;
+        public GoSlice(IntPtr data, long len, long cap)
+        {
+            this.data = data;
+            this.len = len;
+            this.cap = cap;
+        }
+    }
+    public struct GoString
+    {
+        public string msg;
+        public long len;
+        public GoString(string msg, long len)
+        {
+            this.msg = msg;
+            this.len = len;
+        }
+    }
+
+    // Use DllImport to import the Awesome lib.
+    [DllImport(libName)]
+    public static extern int Add(long a, long b);
+
+    [DllImport(libName)]
+    public static extern double Cosine(double a);
+
+    [DllImport(libName)]
+    public static extern void Sort(GoSlice a);
+
+    [DllImport(libName, CharSet = CharSet.Unicode)]
+    public static extern void Log(GoString msg);
+
+    static void Main()
+    {
+        long add = Add(12, 99);
+        double cosine = Cosine(1);
+
+        long[] data = { 77, 12, 5, 99, 28, 23 };
+        IntPtr data_ptr = Marshal.AllocHGlobal(Buffer.ByteLength(data));
+        Marshal.Copy(data, 0, data_ptr, data.Length);
+        var nums = new GoSlice(data_ptr, data.Length, data.Length);
+        Sort(nums);
+        Marshal.Copy(nums.data, data, 0, data.Length);
+
+        string msg = "Hello from C#!";
+        GoString str = new GoString(msg, msg.Length);
+
+        Console.WriteLine("awesome.Add(12,99) = " + add);
+        Console.WriteLine("awesome.Cosine(1) = " + cosine);
+        Console.WriteLine("awesome.Sort(77,12,5,99,28,23): " + string.Join(", ", data));
+        Log(str);
+    }
+}