Fix NullReference exception in IsDisplayClass.

Add IsKnownType helper.

src/AddIns/Debugger/Debugger.AddIn/TreeModel/ValueNode.cs

@@ -123,7 +123,7 @@ namespace Debugger.AddIn.TreeModel
 						this.GetChildren = () => GetArrayChildren(dims, dims);
 					}
 				} else if (val.Type.Kind == TypeKind.Class || val.Type.Kind == TypeKind.Struct) {
-					if (val.Type.FullName == typeof(List<>).FullName) {
+					if (val.Type.IsKnownType(typeof(List<>))) {
 						if ((int)val.GetFieldValue("_size").PrimitiveValue > 0)
 							this.GetChildren = () => GetIListChildren(this.GetValue);
 					} else {
@@ -355,7 +355,7 @@ namespace Debugger.AddIn.TreeModel
 				);
 			}
 			
-			if (shownType.GetAllBaseTypeDefinitions().Any(t => t.FullName == typeof(IList).FullName)) {
+			if (shownType.GetAllBaseTypeDefinitions().Any(t => t.IsKnownType(typeof(IList)))) {
 				yield return new TreeNode(
 					"IList",
 					() => GetIListChildren(GetValue)

src/AddIns/Debugger/Debugger.Core/TypeSystemExtensions.cs

@@ -375,6 +375,16 @@ namespace Debugger
 			return def != null && def.KnownTypeCode == knownType;
 		}
 		
+		public static bool IsKnownType(this IType type, Type knownType)
+		{
+			var def = type.GetDefinition();
+			if (knownType.IsGenericTypeDefinition) {
+				return def != null && def.Compilation.FindType(knownType).Equals(def);
+			} else {
+				return def != null && def.Compilation.FindType(knownType).Equals(type);
+			}
+		}
+		
 		public static IField GetBackingField(this IMethod method)
 		{
 			return null;
@@ -405,7 +415,7 @@ namespace Debugger
 				return true; // Anonymous method or lambda
 			}
 			
-			if (type.GetDefinition().Attributes.Any(a => a.AttributeType.FullName == typeof(System.Runtime.CompilerServices.CompilerGeneratedAttribute).FullName)) {
+			if (type.GetDefinition() != null && type.GetDefinition().Attributes.Any(a => a.AttributeType.IsKnownType(typeof(System.Runtime.CompilerServices.CompilerGeneratedAttribute)))) {
 				if (type.GetAllBaseTypeDefinitions().Any(t => t.FullName == typeof(System.Collections.IEnumerator).FullName)) {
 					return true; // yield
 				}

src/AddIns/Debugger/Debugger.Core/Value.cs

@@ -493,6 +493,9 @@ namespace Debugger
 					return objectInstance.CorObjectValue.GetFieldValue((fieldInfo.DeclaringType).ToCorDebug().GetClass(), fieldInfo.GetMetadataToken());
 				}
 			} catch (COMException e) {
+				// System.Runtime.InteropServices.COMException (0x80131303): A class is not loaded. (Exception from HRESULT: 0x80131303)
+				if ((uint)e.ErrorCode == 0x80131303)
+					throw new GetValueException("Class " + fieldInfo.DeclaringType.FullName + " is not loaded");
 				throw new GetValueException("Can not get value of field", e);
 			}
 		}