Fix QuantityTypeConverter ignoring given CurrentCulture without DisplayAsAttribute (#1083)

Co-authored-by: Andreas Leeb <[email protected]>

Author: AndreasLeeb

UnitsNet.Tests/QuantityTypeConverterTest.cs

@@ -251,6 +251,24 @@ public void ConvertTo_GivenSomeQuantityAndContextWithDisplayAsUnitAttributes_Ret
             Assert.Equal("10 dm", convertedQuantitySpecificCulture);
         }
 
+        [Theory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public void ConvertTo_GivenCurrentCulture_ReturnValueFormattedAccordingToGivenCulture(bool useDisplayAsAttribute)
+        {
+            QuantityTypeConverter<Length> converter = new();
+            var attributes = useDisplayAsAttribute ? new Attribute[] { new DisplayAsUnitAttribute(Units.LengthUnit.Meter) } : Array.Empty<Attribute>();
+            ITypeDescriptorContext context = new TypeDescriptorContext("SomeMemberName", attributes);
+            CultureInfo.CurrentCulture = CultureInfo.GetCultureInfo("de-AT"); // uses comma as decimal separator
+            CultureInfo.CurrentUICulture = CultureInfo.InvariantCulture; // uses dot as decimal separator
+            Length length = Length.FromMeters(1.5);
+            string expectedResult = length.ToString(CultureInfo.CurrentCulture);
+
+            string convertedQuantity = (string)converter.ConvertTo(context, CultureInfo.CurrentCulture, length, typeof(string));
+
+            Assert.Equal(expectedResult, convertedQuantity);
+        }
+
         [Fact]
         public void ConvertFrom_GivenDefaultUnitAttributeWithWrongUnitType_ThrowsArgumentException()
         {

UnitsNet/QuantityTypeConverter.cs

@@ -218,15 +218,22 @@ public override object ConvertTo(ITypeDescriptorContext context, CultureInfo cul
         {
             DisplayAsUnitAttribute? displayAsUnit = GetAttribute<DisplayAsUnitAttribute>(context);
 
-            if (value is IQuantity qvalue && destinationType == typeof(string) && displayAsUnit != null)
+            if (value is not IQuantity qvalue || destinationType != typeof(string))
             {
-                if (displayAsUnit.UnitType != null)
-                    return qvalue.ToUnit(displayAsUnit.UnitType).ToString(displayAsUnit.Format, culture);
-                else
-                    return qvalue.ToString(displayAsUnit.Format, culture);
+                return base.ConvertTo(context, culture, value, destinationType);
+            }
+
+            if (displayAsUnit == null)
+            {
+                return qvalue.ToString(culture);
+            }
+
+            if (displayAsUnit.UnitType == null)
+            {
+                return qvalue.ToString(displayAsUnit.Format, culture);
             }
 
-            return base.ConvertTo(context, culture, value, destinationType);
+            return qvalue.ToUnit(displayAsUnit.UnitType).ToString(displayAsUnit.Format, culture);
         }
     }
 }