Question

我正在尝试使用Roslyn来获取对该属性的支持字段的符号（FieldSymbol）的引用，但是AssociatedPropertyOrEvent为null。这是单元测试失败。

[Test]
public void Get_BackingField_for_Property()
{

    var sourceCode = @" public class Player
                    {
                        private Person _MyPerson;

                        public virtual Person MyPerson
                        {
                            get { return _MyPerson; }
                        }

                        public virtual void Set(Person person)
                        {
                            _MyPerson = person;
                        }
                    }";


    var syntaxTree = SyntaxTree.ParseText(sourceCode);


    var mscorlib = MetadataReference.CreateAssemblyReference(
                                     "mscorlib");


    var compilation = Compilation.Create("HelloWorld")
                    .AddReferences(mscorlib)
                    .AddSyntaxTrees(syntaxTree);

    //var  semanticModel = compilation.GetSemanticModel(syntaxTree);

    var classSymbol =
        compilation.GetTypeByMetadataName("Player");

    Assert.That(classSymbol,Is.Not.Null, "class");

    var propertySymbol = classSymbol.GetMembers().Where(x => x.Kind == SymbolKind.Property);

    Assert.That(propertySymbol, Is.Not.Null, "property");

    var backingField = classSymbol.GetMembers().Where(x=>x.Kind== SymbolKind.Field).Cast<FieldSymbol>().First();

    Assert.That(backingField.AssociatedPropertyOrEvent, Is.Not.Null,"backing field");

更新：对于任何尝试执行相同操作的人来说，INotifyPropertyChaged示例都有代码可以获取属性的支持字段。我修改它以满足我的需要。这是代码

internal static IFieldSymbol GetBackingField(this IPropertySymbol property, ISemanticModel semanticModel)
{
    var propertyDelcarationSyntax = (PropertyDeclarationSyntax)property.DeclaringSyntaxNodes.First();

    var getter = propertyDelcarationSyntax.AccessorList.Accessors.First(a => a.Kind == SyntaxKind.GetAccessorDeclaration);

    return GetBackingFieldFromGetter(getter, semanticModel);
}
private static IFieldSymbol GetBackingFieldFromGetter(AccessorDeclarationSyntax getter, ISemanticModel semanticModel)
{
    // The getter should have a body containing a single return of a backing field.

    if (getter.Body == null)
    {
        throw new Exception("Missing a getter body for property " + semanticModel.GetDeclaredSymbol(getter.Parent).Name);
    }

    var statements = getter.Body.Statements;
    if (statements.Count != 1)
    {
        throw new Exception("Getter body has more then one statement for property " + semanticModel.GetDeclaredSymbol(getter.Parent).Name);
    }

    var returnStatement = statements.Single() as ReturnStatementSyntax;
    if (returnStatement == null || returnStatement.Expression == null)
    {
        throw new Exception("Getter body is missing a return statement for property " + semanticModel.GetDeclaredSymbol(getter.Parent).Name);
    }

    return semanticModel.GetSymbolInfo(returnStatement.Expression).Symbol as IFieldSymbol;
}

Answer 1

AssociatedPropertyOrEvent的文档说：

如果此字段用作自动生成的属性或类字段事件的后备变量，则返回该属性/事件。否则返回null。

由于您的字段与任何autoproperties无关，AssociatedPropertyOrEvent会正确返回null。

一般来说，您所要求的是不可能的，因为可能有许多属性可以访问同一个字段。

Answer 2

您只能使用当前的API进行其他方式。使用GetMembers获取所有这些内容，然后找到AssociatedPropertyOrEvent是您想要的属性的字段。

如何获取属性的后备字段（AssociatedPropertyOrEvent为null）？

2 个答案: