Add C# API for Dolphin CTC models (#2089)

scripts/dotnet/OfflineDolphinModelConfig.cs

@@ -0,0 +1,17 @@
+/// Copyright (c)  2025  Xiaomi Corporation (authors: Fangjun Kuang)
+
+using System.Runtime.InteropServices;
+
+namespace SherpaOnnx
+{
+    [StructLayout(LayoutKind.Sequential)]
+    public struct OfflineDolphinModelConfig
+    {
+        public OfflineDolphinModelConfig()
+        {
+            Model = "";
+        }
+        [MarshalAs(UnmanagedType.LPStr)]
+        public string Model;
+    }
+}

scripts/dotnet/OfflineModelConfig.cs

@@ -26,6 +26,7 @@ namespace SherpaOnnx
             SenseVoice = new OfflineSenseVoiceModelConfig();
             Moonshine = new OfflineMoonshineModelConfig();
             FireRedAsr = new OfflineFireRedAsrModelConfig();
+            Dolphin = new OfflineDolphinModelConfig();
         }
         public OfflineTransducerModelConfig Transducer;
         public OfflineParaformerModelConfig Paraformer;
@@ -58,5 +59,6 @@ namespace SherpaOnnx
         public OfflineSenseVoiceModelConfig SenseVoice;
         public OfflineMoonshineModelConfig Moonshine;
         public OfflineFireRedAsrModelConfig FireRedAsr;
+        public OfflineDolphinModelConfig Dolphin;
     }
 }