Fix #1095: C# decompilation, for flags enums always use hex prefix

ICSharpCode.Decompiler.Tests/CustomAttributes/CustomAttributeTests.cs

@@ -12,13 +12,13 @@ namespace ICSharpCode.Decompiler.Tests.CustomAttributes
 		}
 
 		[Test]
-		public void CustomAttributesMultiTest()
+		public void CustomAttributes()
 		{
 			ValidateFileRoundtrip(@"CustomAttributes/S_CustomAttributes.cs");
 		}
 
 		[Test]
-		public void AssemblyCustomAttributesMultiTest()
+		public void AssemblyCustomAttribute()
 		{
 			ValidateFileRoundtrip(@"CustomAttributes/S_AssemblyCustomAttribute.cs");
 		}

ICSharpCode.Decompiler.Tests/CustomAttributes/S_CustomAttributeSamples.cs

@@ -28,7 +28,7 @@ namespace ParameterLessAttributeUsage
 	[Flags]
 	public enum EnumWithFlagsAttribute
 	{
-		None = 0
+		None = 0x0
 	}
 }
 //$$ AttributeWithEnumArgument

ICSharpCode.Decompiler.Tests/CustomAttributes/S_CustomAttributes.cs

@@ -27,11 +27,11 @@ namespace CustomAttributes
 		public enum EnumWithFlag
 		{
 			All = 0xF,
-			None = 0,
-			Item1 = 1,
-			Item2 = 2,
-			Item3 = 4,
-			Item4 = 8
+			None = 0x0,
+			Item1 = 0x1,
+			Item2 = 0x2,
+			Item3 = 0x4,
+			Item4 = 0x8
 		}
 		[AttributeUsage(AttributeTargets.All)]
 		public class MyAttribute : Attribute

ICSharpCode.Decompiler.Tests/TestCases/Pretty/CompoundAssignmentTest.cs

@@ -26,10 +26,10 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 		[Flags]
 		private enum MyEnum
 		{
-			None = 0,
-			One = 1,
-			Two = 2,
-			Four = 4
+			None = 0x0,
+			One = 0x1,
+			Two = 0x2,
+			Four = 0x4
 		}
 
 		public enum ShortEnum : short

ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs

@@ -1174,7 +1174,7 @@ namespace ICSharpCode.Decompiler.CSharp
 				long initValue = (long)CSharpPrimitiveCast.Cast(TypeCode.Int64, field.ConstantValue, false);
 				if (decompilationContext.CurrentTypeDefinition.Attributes.Any(a => a.AttributeType.FullName == "System.FlagsAttribute")) {
 					enumDec.Initializer = typeSystemAstBuilder.ConvertConstantValue(decompilationContext.CurrentTypeDefinition.EnumUnderlyingType, field.ConstantValue);
-					if (enumDec.Initializer is PrimitiveExpression primitive && initValue > 9)
+					if (enumDec.Initializer is PrimitiveExpression primitive)
 						primitive.SetValue(initValue, $"0x{initValue:X}");
 				} else if (previousValue + 1 != initValue) {
 					enumDec.Initializer = typeSystemAstBuilder.ConvertConstantValue(decompilationContext.CurrentTypeDefinition.EnumUnderlyingType, field.ConstantValue);