Add WASI unit tests for the C# API.

crates/misc/dotnet/tests/TempFile.cs

@@ -0,0 +1,24 @@
+using System;
+using System.IO;
+
+namespace Wasmtime.Tests
+{
+    internal class TempFile : IDisposable
+    {
+        public TempFile()
+        {
+            Path = System.IO.Path.GetTempFileName();
+        }
+
+        public void Dispose()
+        {
+            if (Path != null)
+            {
+                File.Delete(Path);
+                Path = null;
+            }
+        }
+
+        public string Path { get; private set; }
+    }
+}