Fix Tester.DecompileCSharp

ICSharpCode.Decompiler.Tests/Helpers/Tester.cs

@@ -377,7 +377,7 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 
 		public static string DecompileCSharp(string assemblyFileName, DecompilerSettings settings = null)
 		{
-			using (var module = Mono.Cecil.ModuleDefinition.ReadModule(assemblyFileName)) {
+			using (var module = Metadata.UniversalAssemblyResolver.LoadMainModule(assemblyFileName)) {
 				var typeSystem = new DecompilerTypeSystem(module);
 				CSharpDecompiler decompiler = new CSharpDecompiler(typeSystem, settings ?? new DecompilerSettings());
 				decompiler.AstTransforms.Insert(0, new RemoveEmbeddedAtttributes());

ICSharpCode.Decompiler/Metadata/Dom.cs

@@ -87,7 +87,7 @@ namespace ICSharpCode.Decompiler.Metadata
 		Net_4_0
 	}
 
-	public class PEFile
+	public class PEFile : IDisposable
 	{
 		public string FileName { get; }
 		public PEReader Reader { get; }
@@ -156,6 +156,11 @@ namespace ICSharpCode.Decompiler.Metadata
 				yield return new Resource(this, h);
 			}
 		}
+
+		public void Dispose()
+		{
+			Reader.Dispose();
+		}
 	}
 
 	public enum ResourceType

ICSharpCode.Decompiler/Metadata/UniversalAssemblyResolver.cs

@@ -61,7 +61,7 @@ namespace ICSharpCode.Decompiler.Metadata
 		{
 			var resolver = new UniversalAssemblyResolver(mainAssemblyFileName, throwOnError);
 
-			var module = new PEReader(new FileStream(mainAssemblyFileName, FileMode.Open), inMemory ? PEStreamOptions.PrefetchEntireImage : PEStreamOptions.Default);
+			var module = new PEReader(new FileStream(mainAssemblyFileName, FileMode.Open, FileAccess.Read), inMemory ? PEStreamOptions.PrefetchEntireImage : PEStreamOptions.Default);
 
 			resolver.TargetFramework = module.DetectTargetFrameworkId();