Split online.cs and offline.csFile (#941)

Co-authored-by: 东风破 <birdfishs@163.com>

scripts/dotnet/SpokenLanguageIdentificationResult.cs

@@ -0,0 +1,46 @@
+/// Copyright (c)  2024.5 by 东风破
+
+using System.Linq;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using System.Text;
+using System;
+
+namespace SherpaOnnx
+{
+    public class SpokenLanguageIdentificationResult
+    {
+        public SpokenLanguageIdentificationResult(IntPtr handle)
+        {
+            Impl impl = (Impl)Marshal.PtrToStructure(handle, typeof(Impl));
+
+            // PtrToStringUTF8() requires .net standard 2.1
+            // _text = Marshal.PtrToStringUTF8(impl.Text);
+
+            int length = 0;
+
+            unsafe
+            {
+                byte* buffer = (byte*)impl.Lang;
+                while (*buffer != 0)
+                {
+                    ++buffer;
+                    length += 1;
+                }
+            }
+
+            byte[] stringBuffer = new byte[length];
+            Marshal.Copy(impl.Lang, stringBuffer, 0, length);
+            _lang = Encoding.UTF8.GetString(stringBuffer);
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        struct Impl
+        {
+            public IntPtr Lang;
+        }
+
+        private String _lang;
+        public String Lang => _lang;
+    }
+}