Do not use a fractional representation, if it has less than 6 significant digits.

ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs

@@ -949,30 +949,24 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			ICompilation compilation = type.GetDefinition().Compilation;
 			Expression expr = null;
 
+			string str;
 			if (isDouble) {
 				if (Math.Floor((double)constantValue) == (double)constantValue) {
 					expr = new PrimitiveExpression(constantValue);
 				}
+
+				str = ((double)constantValue).ToString("r");
 			} else {
 				if (Math.Floor((float)constantValue) == (float)constantValue) {
 					expr = new PrimitiveExpression(constantValue);
 				}
-			}
 
-			if (expr == null) {
+				str = ((float)constantValue).ToString("r");
-				(long num, long den) = isDouble
-					? FractionApprox((double)constantValue, MAX_DENOMINATOR)
-					: FractionApprox((float)constantValue, MAX_DENOMINATOR);
-
-				if (IsValidFraction(num, den) && IsEqual(num, den, constantValue, isDouble) && Math.Abs(num) != 1 && Math.Abs(den) != 1) {
-					var left = MakeConstant(type, num);
-					var right = MakeConstant(type, den);
-					return new BinaryOperatorExpression(left, BinaryOperatorType.Divide, right).WithoutILInstruction()
-						.WithRR(new ConstantResolveResult(type, constantValue));
-				}
 			}
 
-			if (expr == null && UseSpecialConstants) {
+			bool useFraction = (str.Length - (str.StartsWith("-", StringComparison.OrdinalIgnoreCase) ? 2 : 1) > 5);
+
+			if (useFraction && expr == null && UseSpecialConstants) {
 				IType mathType;
 				if (isDouble)
 					mathType = compilation.FindType(typeof(Math));
@@ -984,6 +978,19 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 					?? TryExtractExpression(mathType, type, constantValue, "E", isDouble);
 			}
 
+			if (useFraction && expr == null) {
+				(long num, long den) = isDouble
+					? FractionApprox((double)constantValue, MAX_DENOMINATOR)
+					: FractionApprox((float)constantValue, MAX_DENOMINATOR);
+
+				if (IsValidFraction(num, den) && IsEqual(num, den, constantValue, isDouble) && Math.Abs(num) != 1 && Math.Abs(den) != 1) {
+					var left = MakeConstant(type, num);
+					var right = MakeConstant(type, den);
+					return new BinaryOperatorExpression(left, BinaryOperatorType.Divide, right).WithoutILInstruction()
+						.WithRR(new ConstantResolveResult(type, constantValue));
+				}
+			}
+
 			if (expr == null)
 				expr = new PrimitiveExpression(constantValue);