Provide better exceptions and messages in case of errors.

ICSharpCode.Decompiler/IL/ILReader.cs

@@ -1589,7 +1589,7 @@ ILInstruction LdToken(EntityHandle token)
 				return new LdTypeToken(typeSystem.ResolveAsType(token));
 			if (token.Kind.IsMemberKind())
 				return new LdMemberToken(typeSystem.ResolveAsMember(token));
-			throw new NotImplementedException();
+			throw new BadImageFormatException("Invalid metadata token for ldtoken instruction.");
 		}
 	}
 }

ICSharpCode.Decompiler/IL/Instructions/ILFunction.cs

@@ -100,7 +100,7 @@ internal override void CheckInvariant(ILPhase phase)
 
 		void CloneVariables()
 		{
-			throw new NotImplementedException();
+			throw new NotSupportedException("ILFunction.CloneVariables is currently not supported!");
 		}
 
 		public override void WriteTo(ITextOutput output, ILAstWritingOptions options)

ICSharpCode.Decompiler/Metadata/PEFile.cs

@@ -43,6 +43,8 @@ public PEFile(string fileName, PEReader reader)
 		{
 			this.FileName = fileName ?? throw new ArgumentNullException(nameof(fileName));
 			this.Reader = reader ?? throw new ArgumentNullException(nameof(reader));
+			if (!reader.HasMetadata)
+				throw new ArgumentException("PE file does not contain any metadata!");
 			this.Metadata = reader.GetMetadataReader();
 		}
 

ILSpy.BamlDecompiler/Ricciolo.StylesExplorer.MarkupReflection/BamlBinaryReader.cs

@@ -8,15 +8,15 @@ namespace Ricciolo.StylesExplorer.MarkupReflection
 {
 	internal class BamlBinaryReader : BinaryReader
 	{
-		// Methods
 		public BamlBinaryReader(Stream stream)
 			: base(stream)
 		{
 		}
 
 		public virtual double ReadCompressedDouble()
 		{
-			switch (this.ReadByte()) {
+			byte b = this.ReadByte();
+			switch (b) {
 				case 1:
 					return 0;
 				case 2:
@@ -27,8 +27,9 @@ public virtual double ReadCompressedDouble()
 					return ReadInt32() * 1E-06;
 				case 5:
 					return this.ReadDouble();
+				default:
+					throw new BadImageFormatException($"Unexpected byte sequence in ReadCompressedDouble: 0x{b:x}");
 			}
-			throw new NotSupportedException();
 		}
 
 		public int ReadCompressedInt32()

ILSpy.BamlDecompiler/Ricciolo.StylesExplorer.MarkupReflection/XmlBamlReader.cs

@@ -467,7 +467,7 @@ void EnsureInit()
 				int s = reader.ReadInt32();
 				int t = reader.ReadInt32();
 				if (((r != 0x600000) || (s != 0x600000)) || (t != 0x600000))
-					throw new NotSupportedException();
+					throw new BadImageFormatException("Magic value mismatch!");
 
 				initialized = true;
 			}

ILSpy/Analyzers/AnalyzeContextMenuEntry.cs

@@ -85,7 +85,7 @@ public static void Analyze(IEntity entity)
 					AnalyzerTreeView.Instance.ShowOrFocus(new AnalyzedEventTreeNode(ed));
 					break;
 				default:
-					throw new NotSupportedException();
+					throw new ArgumentOutOfRangeException(nameof(entity), $"Entity {entity.GetType().FullName} is not supported.");
 			}
 		}
 	}

ILSpy/Analyzers/AnalyzerSearchTreeNode.cs

@@ -68,9 +68,13 @@ protected IEnumerable<AnalyzerTreeNode> FetchChildren(CancellationToken ct)
 			}
 		}
 
-		AnalyzerTreeNode EntityTreeNodeFactory(IEntity result)
+		AnalyzerTreeNode EntityTreeNodeFactory(IEntity entity)
 		{
-			switch (result) {
+			if (entity == null) {
+				throw new ArgumentNullException(nameof(entity));
+			}
+
+			switch (entity) {
 				case ITypeDefinition td:
 					return new AnalyzedTypeTreeNode(td) {
 						Language = this.Language
@@ -92,7 +96,7 @@ AnalyzerTreeNode EntityTreeNodeFactory(IEntity result)
 						Language = this.Language
 					};
 				default:
-					throw new NotSupportedException();
+					throw new ArgumentOutOfRangeException(nameof(entity), $"Entity {entity.GetType().FullName} is not supported.");
 			}
 		}
 

ILSpy/Images/Images.cs

@@ -168,7 +168,7 @@ protected override ImageSource GetBaseImage(TypeIcon icon)
 						baseImage = Images.StaticClass;
 						break;
 					default:
-						throw new NotSupportedException();
+						throw new ArgumentOutOfRangeException(nameof(icon), $"TypeIcon.{icon} is not supported!");
 				}
 
 				return baseImage;
@@ -238,7 +238,7 @@ protected override ImageSource GetBaseImage(MemberIcon icon)
 						baseImage = Images.Event;
 						break;
 					default:
-						throw new NotSupportedException();
+						throw new ArgumentOutOfRangeException(nameof(icon), $"MemberIcon.{icon} is not supported!");
 				}
 
 				return baseImage;
@@ -303,7 +303,7 @@ private static ImageSource GetOverlayImage(AccessOverlayIcon overlay)
 						overlayImage = Images.OverlayCompilerControlled;
 						break;
 					default:
-						throw new NotSupportedException();
+						throw new ArgumentOutOfRangeException(nameof(overlay), $"AccessOverlayIcon.{overlay} is not supported!");
 				}
 				return overlayImage;
 			}