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

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

scripts/dotnet/OfflineStream.cs

@@ -0,0 +1,72 @@
+/// 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 OfflineStream : IDisposable
+    {
+        public OfflineStream(IntPtr p)
+        {
+            _handle = new HandleRef(this, p);
+        }
+
+        public void AcceptWaveform(int sampleRate, float[] samples)
+        {
+            AcceptWaveform(Handle, sampleRate, samples, samples.Length);
+        }
+
+        public OfflineRecognizerResult Result
+        {
+            get
+            {
+                IntPtr h = GetResult(_handle.Handle);
+                OfflineRecognizerResult result = new OfflineRecognizerResult(h);
+                DestroyResult(h);
+                return result;
+            }
+        }
+
+        ~OfflineStream()
+        {
+            Cleanup();
+        }
+
+        public void Dispose()
+        {
+            Cleanup();
+            // Prevent the object from being placed on the
+            // finalization queue
+            System.GC.SuppressFinalize(this);
+        }
+
+        private void Cleanup()
+        {
+            DestroyOfflineStream(Handle);
+
+            // Don't permit the handle to be used again.
+            _handle = new HandleRef(this, IntPtr.Zero);
+        }
+
+        private HandleRef _handle;
+        public IntPtr Handle => _handle.Handle;
+
+        [DllImport(Dll.Filename)]
+        private static extern void DestroyOfflineStream(IntPtr handle);
+
+        [DllImport(Dll.Filename, EntryPoint = "AcceptWaveformOffline")]
+        private static extern void AcceptWaveform(IntPtr handle, int sampleRate, float[] samples, int n);
+
+        [DllImport(Dll.Filename, EntryPoint = "GetOfflineStreamResult")]
+        private static extern IntPtr GetResult(IntPtr handle);
+
+        [DllImport(Dll.Filename, EntryPoint = "DestroyOfflineRecognizerResult")]
+        private static extern void DestroyResult(IntPtr handle);
+    }
+
+}