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Merged
RussKie merged 2 commits into from
Jan 17, 2020
Merged

Improve PaddingConverter CreateInstance implementation #2679

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6e6e23e
Accept null context in PaddingConverter.
weltkante Jan 9, 2020
f2c4279
Update tests to match expectations
weltkante Jan 17, 2020
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37 changes: 20 additions & 17 deletions src/System.Windows.Forms.Primitives/src/System/Windows/Forms/PaddingConverter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -122,32 +122,35 @@ public override object ConvertTo(ITypeDescriptorContext context, CultureInfo cul

public override object CreateInstance(ITypeDescriptorContext context, IDictionary propertyValues)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
if (propertyValues == null)
{
throw new ArgumentNullException(nameof(propertyValues));
}

Padding original = (Padding)context.PropertyDescriptor.GetValue(context.Instance);
var original = context?.PropertyDescriptor?.GetValue(context.Instance);
try
{
int all = (int)propertyValues[nameof(Padding.All)];
if (original.All != all)
// When incrementally changing an existing Padding instance e.g. through a PropertyGrid
// the expected behavior is that a change of Padding.All will override the now outdated
// other properties of the original padding.
//
// If we are not incrementally changing an existing instance (i.e. have no original value)
// then we can just select the individual components passed in the full set of properties
// and the Padding constructor will determine whether they are all the same or not.

if (original is Padding originalPadding)
{
return new Padding(all);
}
else
{
return new Padding(
(int)propertyValues[nameof(Padding.Left)],
(int)propertyValues[nameof(Padding.Top)],
(int)propertyValues[nameof(Padding.Right)],
(int)propertyValues[nameof(Padding.Bottom)]
);
int all = (int)propertyValues[nameof(Padding.All)];
if (originalPadding.All != all)
return new Padding(all);
}

return new Padding(
(int)propertyValues[nameof(Padding.Left)],
(int)propertyValues[nameof(Padding.Top)],
(int)propertyValues[nameof(Padding.Right)],
(int)propertyValues[nameof(Padding.Bottom)]
);
}
catch (InvalidCastException invalidCast)
{
Expand Down
22 changes: 18 additions & 4 deletions src/System.Windows.Forms/tests/UnitTests/System/Windows/Forms/PaddingConverterTests.cs
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Expand Up @@ -157,10 +157,21 @@ public void PaddingConverter_CreateInstance_ValidPropertyValuesAll_ReturnsExpect
}

[Fact]
public void PaddingConverter_CreateInstance_NullContext_ThrowsArgumentNullException()
public void PaddingConverter_CreateInstance_ValidPropertyValuesNullContext_ReturnsExpected()
{
var converter = new PaddingConverter();
Assert.Throws<ArgumentNullException>("context", () => converter.CreateInstance(null, new Dictionary<string, object>()));
Padding expected = new Padding(1, 2, 3, 4);
Padding padding = Assert.IsType<Padding>(converter.CreateInstance(
null, new Dictionary<string, object>
{
{nameof(Padding.All), expected.All},
{nameof(Padding.Left), expected.Left},
{nameof(Padding.Top), expected.Top},
{nameof(Padding.Right), expected.Right},
{nameof(Padding.Bottom), expected.Bottom}
})
);
Assert.Equal(expected, padding);
}

[Fact]
Expand Down Expand Up @@ -355,7 +366,7 @@ public void PaddingConverter_CreateInstance_InvalidPropertyValueType_ThrowsArgum
}

[Fact]
public void PaddingConverter_CreateInstance_InvalidInstanceType_ThrowsInvalidCastException()
public void PaddingConverter_CreateInstance_UnknownInstanceType_ReturnsExpected()
{
var converter = new PaddingConverter();
var mockContext = new Mock<ITypeDescriptorContext>(MockBehavior.Strict);
Expand All @@ -374,7 +385,10 @@ public void PaddingConverter_CreateInstance_InvalidInstanceType_ThrowsInvalidCas
{nameof(Padding.Right), 3},
{nameof(Padding.Bottom), 4},
};
Assert.Throws<InvalidCastException>(() => converter.CreateInstance(mockContext.Object, propertyValues));

Padding expected = new Padding(2, 2, 3, 4);
Padding padding = Assert.IsType<Padding>(converter.CreateInstance(mockContext.Object, propertyValues));
Assert.Equal(expected, padding);
}

[Fact]
Expand Down