Fix NullReferenceException in QuantityTypeConverter (#755) (#756)

Author: WalkerCodeRanger

UnitsNet.Tests/Helpers/TypeDescriptorContext.cs

@@ -1,15 +1,13 @@
-// Licensed under MIT No Attribution, see LICENSE file at the root.
+// Licensed under MIT No Attribution, see LICENSE file at the root.
 // Copyright 2013 Andreas Gullberg Larsen ([email protected]). Maintained at https://github.com/angularsen/UnitsNet.
 
 using System;
-using System.Collections.Generic;
 using System.ComponentModel;
-using System.Text;
 
 namespace UnitsNet.Tests.Helpers
 {
     /// <summary>
-    /// Is used to imitate e property with attributes
+    /// Is used to imitate a property with attributes
     /// </summary>
     public class TypeDescriptorContext : ITypeDescriptorContext
     {
@@ -57,6 +55,10 @@ public TypeDescriptorContext(string name, Attribute[] attributes)
             PropertyDescriptor = new PropertyDescriptor_(name, attributes);
         }
 
+        public TypeDescriptorContext()
+        {
+        }
+
         public IContainer Container => throw new NotImplementedException();
 
         public object Instance => throw new NotImplementedException();

UnitsNet.Tests/QuantityTypeConverterTest.cs

@@ -1,4 +1,4 @@
-// Licensed under MIT No Attribution, see LICENSE file at the root.
+// Licensed under MIT No Attribution, see LICENSE file at the root.
 // Copyright 2013 Andreas Gullberg Larsen ([email protected]). Maintained at https://github.com/angularsen/UnitsNet.
 
 using System;
@@ -166,7 +166,7 @@ public void ConvertTo_GivenStringType_ReturnsQuantityString()
         }
 
         [Fact]
-        public void ConvertTo_GivenSomeQuantitysAndContextWithNoAttributes_ReturnsQuantityStringInUnitOfQuantity()
+        public void ConvertTo_GivenSomeQuantityAndContextWithNoAttributes_ReturnsQuantityStringInUnitOfQuantity()
         {
             var converter = new QuantityTypeConverter<Length>();
             ITypeDescriptorContext context = new TypeDescriptorContext("SomeMemberName", new Attribute[] { });
@@ -178,7 +178,19 @@ public void ConvertTo_GivenSomeQuantitysAndContextWithNoAttributes_ReturnsQuanti
         }
 
         [Fact]
-        public void ConvertTo_TestDisplayAsFormatting_ReturnsQuantityStringWithDisplayUnitDefaultFormating()
+        public void ConvertTo_GivenSomeQuantityAndContextWithoutProperty_ReturnsQuantityStringInUnitOfQuantity()
+        {
+            var converter = new QuantityTypeConverter<Length>();
+            ITypeDescriptorContext context = new TypeDescriptorContext();
+            Length length = Length.FromMeters(1);
+
+            string convertedQuantity = (string)converter.ConvertTo(context, culture, length, typeof(string));
+
+            Assert.Equal("1 m", convertedQuantity);
+        }
+
+        [Fact]
+        public void ConvertTo_TestDisplayAsFormatting_ReturnsQuantityStringWithDisplayUnitDefaultFormatting()
         {
             var converter = new QuantityTypeConverter<Length>();
             ITypeDescriptorContext context = new TypeDescriptorContext("SomeMemberName", new Attribute[]
@@ -193,7 +205,7 @@ public void ConvertTo_TestDisplayAsFormatting_ReturnsQuantityStringWithDisplayUn
         }
 
         [Fact]
-        public void ConvertTo_TestDisplayAsFormatting_ReturnsQuantityStringWithDisplayUnitFormateAsValueOnly()
+        public void ConvertTo_TestDisplayAsFormatting_ReturnsQuantityStringWithDisplayUnitFormatAsValueOnly()
         {
             var converter = new QuantityTypeConverter<Length>();
             ITypeDescriptorContext context = new TypeDescriptorContext("SomeMemberName", new Attribute[]
@@ -208,7 +220,7 @@ public void ConvertTo_TestDisplayAsFormatting_ReturnsQuantityStringWithDisplayUn
         }
 
         [Fact]
-        public void ConvertTo_TestDisplayAsFormattingWithoutDefinedUnit_ReturnsQuantityStringWithQuantetiesUnitAndFormatedAsValueOnly()
+        public void ConvertTo_TestDisplayAsFormattingWithoutDefinedUnit_ReturnsQuantityStringWithQuantityUnitAndFormattedAsValueOnly()
         {
             var converter = new QuantityTypeConverter<Length>();
             ITypeDescriptorContext context = new TypeDescriptorContext("SomeMemberName", new Attribute[]
@@ -223,7 +235,7 @@ public void ConvertTo_TestDisplayAsFormattingWithoutDefinedUnit_ReturnsQuantityS
         }
 
         [Fact]
-        public void ConvertTo_GivenSomeQuantitysAndContextWithDisplayAsUnitAttributes_ReturnsQuantityStringInSpecifiedDisplayUnit()
+        public void ConvertTo_GivenSomeQuantityAndContextWithDisplayAsUnitAttributes_ReturnsQuantityStringInSpecifiedDisplayUnit()
         {
             var converter = new QuantityTypeConverter<Length>();
             ITypeDescriptorContext context = new TypeDescriptorContext("SomeMemberName", new Attribute[]

UnitsNet/QuantityTypeConverter.cs

@@ -141,7 +141,7 @@ public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceT
         private static TAttribute GetAttribute<TAttribute>(ITypeDescriptorContext context) where TAttribute : UnitAttributeBase
         {
             TAttribute attribute = null;
-            AttributeCollection ua = context?.PropertyDescriptor.Attributes;
+            AttributeCollection ua = context?.PropertyDescriptor?.Attributes;
 
             attribute = (TAttribute)ua?[typeof(TAttribute)];