C#: Address review comments

Author: hvitved

csharp/extractor/Semmle.Extraction.CSharp/CompilerVersion.cs

@@ -55,21 +55,21 @@ public CompilerVersion(Options options)
                 var versionInfo = FileVersionInfo.GetVersionInfo(SpecifiedCompiler);
 
                 var compilerDir = Path.GetDirectoryName(SpecifiedCompiler);
-                var known_compiler_names = new Dictionary<string, string>
+                var knownCompilerNames = new Dictionary<string, string>
                 {
                     { "csc.exe", "Microsoft" },
                     { "csc2.exe", "Microsoft" },
                     { "csc.dll", "Microsoft" },
                     { "mcs.exe", "Novell" }
                 };
-                var mscorlib_exists = File.Exists(Path.Combine(compilerDir, "mscorlib.dll"));
+                var mscorlibExists = File.Exists(Path.Combine(compilerDir, "mscorlib.dll"));
 
-                if (specifiedFramework == null && mscorlib_exists)
+                if (specifiedFramework == null && mscorlibExists)
                 {
                     specifiedFramework = compilerDir;
                 }
 
-                if (!known_compiler_names.TryGetValue(versionInfo.OriginalFilename, out var vendor))
+                if (!knownCompilerNames.TryGetValue(versionInfo.OriginalFilename, out var vendor))
                 {
                     SkipExtractionBecause("the compiler name is not recognised");
                     return;

csharp/extractor/Semmle.Extraction/TrapWriter.cs

@@ -211,11 +211,14 @@ public void Emit(ITrapEmitter emitter)
         /// </summary>
         static string ComputeHash(string filePath)
         {
-            using (var fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read))
+            using (var fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read))
             using (var shaAlg = new SHA256Managed())
             {
                 var sha = shaAlg.ComputeHash(fileStream);
-                return Convert.ToBase64String(sha);
+                var hex = new StringBuilder(sha.Length * 2);
+                foreach (var b in sha)
+                    hex.AppendFormat("{0:x2}", b);
+                return hex.ToString();
             }
         }