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Fix null URI handling in generated dependency property setters #818

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Merged
Sergio0694 merged 2 commits into from
Sep 24, 2026
Merged

Fix null URI handling in generated dependency property setters #818

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511a88b
Fix null URI dependency property setters
Sergio0694 Sep 22, 2026
58cbe62
Use full-output dependency property generator tests
Sergio0694 Sep 22, 2026
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25 changes: 16 additions & 9 deletions ...olkit.DependencyPropertyGenerator.SourceGenerators/DependencyPropertyGenerator.Execute.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -802,6 +802,14 @@ static string GetExpressionWithTrailingSpace(Accessibility accessibility)
{
string oldValueTypeNameAsNullable = GetOldValueTypeNameAsNullable(propertyInfo);

// These helpers reject null values, and empty 'string' values also marshal to a null 'HSTRING'
string? xamlBindingHelperFallbackCondition = propertyInfo.XamlBindingHelperSetMethodName switch
{
"SetPropertyFromString" => "value is null || value.Length == 0",
"SetPropertyFromUri" => "value is null",
_ => null
};

// Declare the property
writer.WriteLine(skipIfPresent: true);
writer.WriteLine("/// <inheritdoc/>");
Expand Down Expand Up @@ -845,19 +853,18 @@ static string GetExpressionWithTrailingSpace(Accessibility accessibility)
field = value;
""", isMultiline: true);

// If the property is of type 'string', we need a special path. That is because 'XamlBindingHelper.SetPropertyFromString'
// doesn't work correctly for 'null' or empty strings, so we need to fall back to 'SetValue' in those cases.
if (propertyInfo.TypeName == "string")
// Fall back to 'SetValue' for values rejected by the selected helper
if (xamlBindingHelperFallbackCondition is not null)
{
writer.Write($$"""

if (value is null || value.Length == 0)
if ({{xamlBindingHelperFallbackCondition}})
{
SetValue({{propertyInfo.PropertyName}}Property, value);
}
else
{
global::{{WellKnownTypeNames.XamlBindingHelper(propertyInfo.UseWindowsUIXaml)}}.SetPropertyFromString(this, {{propertyInfo.PropertyName}}Property, value);
global::{{WellKnownTypeNames.XamlBindingHelper(propertyInfo.UseWindowsUIXaml)}}.{{propertyInfo.XamlBindingHelperSetMethodName}}(this, {{propertyInfo.PropertyName}}Property, value);
}

On{{propertyInfo.PropertyName}}Changed(value);
Expand Down Expand Up @@ -942,21 +949,21 @@ static string GetExpressionWithTrailingSpace(Accessibility accessibility)
}
""", isMultiline: true);

// For 'string' properties, we need a specialized path (see comment in the local caching branch above)
if (propertyInfo.TypeName == "string")
// Match the 'string' and 'Uri' fallback from the local caching branch
if (xamlBindingHelperFallbackCondition is not null)
{
writer.WriteLine($$"""
{{GetExpressionWithTrailingSpace(propertyInfo.SetterAccessibility)}}set
{
On{{propertyInfo.PropertyName}}Set(ref value);

if (value is null || value.Length == 0)
if ({{xamlBindingHelperFallbackCondition}})
{
SetValue({{propertyInfo.PropertyName}}Property, value);
}
else
{
global::{{WellKnownTypeNames.XamlBindingHelper(propertyInfo.UseWindowsUIXaml)}}.SetPropertyFromString(this, {{propertyInfo.PropertyName}}Property, value);
global::{{WellKnownTypeNames.XamlBindingHelper(propertyInfo.UseWindowsUIXaml)}}.{{setMethodName}}(this, {{propertyInfo.PropertyName}}Property, value);
}

On{{propertyInfo.PropertyName}}Changed(value);
Expand Down
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