diff --git a/csharp/src/Microsoft.ML.OnnxRuntime/InferenceSession.cs b/csharp/src/Microsoft.ML.OnnxRuntime/InferenceSession.cs
index 0310eb7db0..068fae6f75 100644
--- a/csharp/src/Microsoft.ML.OnnxRuntime/InferenceSession.cs
+++ b/csharp/src/Microsoft.ML.OnnxRuntime/InferenceSession.cs
@@ -215,11 +215,7 @@ namespace Microsoft.ML.OnnxRuntime
         {
             var envHandle = OnnxRuntime.Handle;
             var session = IntPtr.Zero;
-
-            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
-                NativeApiStatus.VerifySuccess(NativeMethods.OrtCreateSession(envHandle, System.Text.Encoding.Unicode.GetBytes(modelPath), options.Handle, out session));
-            else
-                NativeApiStatus.VerifySuccess(NativeMethods.OrtCreateSession(envHandle, System.Text.Encoding.UTF8.GetBytes(modelPath), options.Handle, out session));
+            NativeApiStatus.VerifySuccess(NativeMethods.OrtCreateSession(envHandle, NativeMethods.GetPlatformSerializedString(modelPath), options.Handle, out session));
 
             InitWithSessionHandle(session, options);
         }
diff --git a/csharp/src/Microsoft.ML.OnnxRuntime/NativeMethods.cs b/csharp/src/Microsoft.ML.OnnxRuntime/NativeMethods.cs
index a7cb482d7d..18bcb1b50d 100644
--- a/csharp/src/Microsoft.ML.OnnxRuntime/NativeMethods.cs
+++ b/csharp/src/Microsoft.ML.OnnxRuntime/NativeMethods.cs
@@ -364,10 +364,10 @@ namespace Microsoft.ML.OnnxRuntime
         ExecutionMode execution_mode);
         public static DOrtSetSessionExecutionMode OrtSetSessionExecutionMode;
 
-        public delegate IntPtr /*(OrtStatus*)*/ DOrtSetOptimizedModelFilePath(IntPtr /* OrtSessionOptions* */ options, [MarshalAs(UnmanagedType.LPWStr)]string optimizedModelFilepath);
+        public delegate IntPtr /*(OrtStatus*)*/ DOrtSetOptimizedModelFilePath(IntPtr /* OrtSessionOptions* */ options, byte[] optimizedModelFilepath);
         public static DOrtSetOptimizedModelFilePath OrtSetOptimizedModelFilePath;
 
-        public delegate IntPtr /*(OrtStatus*)*/ DOrtEnableProfiling(IntPtr /* OrtSessionOptions* */ options, string profilePathPrefix);
+        public delegate IntPtr /*(OrtStatus*)*/ DOrtEnableProfiling(IntPtr /* OrtSessionOptions* */ options, byte[] profilePathPrefix);
         public static DOrtEnableProfiling OrtEnableProfiling;
 
         public delegate IntPtr /*(OrtStatus*)*/ DOrtDisableProfiling(IntPtr /* OrtSessionOptions* */ options);
@@ -659,5 +659,13 @@ namespace Microsoft.ML.OnnxRuntime
         public static DOrtReleaseValue OrtReleaseValue;
 
         #endregion
+
+        public static byte[] GetPlatformSerializedString(string str)
+        {
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+                return System.Text.Encoding.Unicode.GetBytes(str + Char.MinValue);
+            else
+                return System.Text.Encoding.UTF8.GetBytes(str + Char.MinValue);
+        }
     } //class NativeMethods
 } //namespace
diff --git a/csharp/src/Microsoft.ML.OnnxRuntime/SessionOptions.cs b/csharp/src/Microsoft.ML.OnnxRuntime/SessionOptions.cs
index 1eb0984270..5a34d2dca5 100644
--- a/csharp/src/Microsoft.ML.OnnxRuntime/SessionOptions.cs
+++ b/csharp/src/Microsoft.ML.OnnxRuntime/SessionOptions.cs
@@ -201,7 +201,7 @@ namespace Microsoft.ML.OnnxRuntime
             {
                 if (!_enableProfiling && value)
                 {
-                    NativeApiStatus.VerifySuccess(NativeMethods.OrtEnableProfiling(_nativePtr, ProfileOutputPathPrefix));
+                    NativeApiStatus.VerifySuccess(NativeMethods.OrtEnableProfiling(_nativePtr, NativeMethods.GetPlatformSerializedString(ProfileOutputPathPrefix)));
                     _enableProfiling = true;
                 }
                 else if (_enableProfiling && !value)
@@ -226,7 +226,7 @@ namespace Microsoft.ML.OnnxRuntime
             {
                 if (value != _optimizedModelFilePath)
                 {
-                    NativeApiStatus.VerifySuccess(NativeMethods.OrtSetOptimizedModelFilePath(_nativePtr, value));
+                    NativeApiStatus.VerifySuccess(NativeMethods.OrtSetOptimizedModelFilePath(_nativePtr, NativeMethods.GetPlatformSerializedString(value)));
                     _optimizedModelFilePath = value;
                 }
             }
diff --git a/csharp/test/Microsoft.ML.OnnxRuntime.Tests/InferenceTest.cs b/csharp/test/Microsoft.ML.OnnxRuntime.Tests/InferenceTest.cs
index 4072fd3f26..c566e8853a 100644
--- a/csharp/test/Microsoft.ML.OnnxRuntime.Tests/InferenceTest.cs
+++ b/csharp/test/Microsoft.ML.OnnxRuntime.Tests/InferenceTest.cs
@@ -344,6 +344,8 @@ namespace Microsoft.ML.OnnxRuntime.Tests
             if (System.Environment.Is64BitProcess == false)
             {
                 skipModels["test_vgg19"] = "Get preallocated buffer for initializer conv4_4_b_0 failed";
+                skipModels["tf_pnasnet_large"] = "Get preallocated buffer for initializer ConvBnFusion_BN_B_cell_5/comb_iter_1/left/bn_sep_7x7_1/beta:0_203 failed";
+                skipModels["tf_nasnet_large"] = "Get preallocated buffer for initializer ConvBnFusion_BN_B_cell_11/beginning_bn/beta:0_331 failed";
             }
 
             return skipModels;
@@ -390,7 +392,7 @@ namespace Microsoft.ML.OnnxRuntime.Tests
         }
 
 
-        [Theory(Skip = "TestPreTrainedModels is flaky and is blocking CI build progress. Enable it once this is fixed.")]
+        [Theory]
         [MemberData(nameof(GetModelsForTest))]
         [MemberData(nameof(GetSkippedModelForTest), Skip = "Skipped due to Error, please fix the error and enable the test")]
         private void TestPreTrainedModels(string opset, string modelName)