在CodeRefactoringProvider中使用ArgumentList的ObjectCreationExpression

Question

我正在尝试使用.NET编译器平台(roslyn)实现代码重构.但是,出于某种原因,我不能使ObjectCreationExpression与ArgumentList一起使用.这是我的方法(整个代码可以在这里找到):

private aync Task<Document> AddGuardAsync(Document document, ParameterSyntax parameter, BaseMethodDeclarationSyntax methodDeclaration, CancellationToken cancellationToken)
{
    BinaryExpressionSyntax binaryExpression = SyntaxFactory.BinaryExpression(SyntaxKind.EqualsExpression,
        SyntaxFactory.IdentifierName(parameter.Identifier),
        SyntaxFactory.LiteralExpression(SyntaxKind.NullLiteralExpression));

    NameOfExpressionSyntax nameOfExp = SyntaxFactory.NameOfExpression(
        "nameof",
        SyntaxFactory.ParseTypeName(parameter.Identifier.Text));

    SeparatedSyntaxList<ArgumentSyntax> argsList = new SeparatedSyntaxList<ArgumentSyntax>();
    argsList.Add(SyntaxFactory.Argument(nameOfExp));

    ObjectCreationExpressionSyntax objectCreationEx = SyntaxFactory.ObjectCreationExpression(
        SyntaxFactory.ParseTypeName(nameof(ArgumentNullException)), 
        SyntaxFactory.ArgumentList(argsList),
        null);

    ThrowStatementSyntax throwStatement = SyntaxFactory.ThrowStatement(objectCreationEx);
    IfStatementSyntax ifStatement = SyntaxFactory
        .IfStatement(SyntaxFactory.Token(SyntaxKind.IfKeyword), SyntaxFactory.Token(SyntaxKind.OpenParenToken), binaryExpression, SyntaxFactory.Token(SyntaxKind.CloseParenToken), throwStatement, null)
        .WithAdditionalAnnotations(Formatter.Annotation);

    SyntaxNode root = await document.GetSyntaxRootAsync(cancellationToken);
    SyntaxNode newRoot = root.InsertNodesBefore(methodDeclaration.Body.ChildNodes().First(), new[] { ifStatement });

    return document.WithSyntaxRoot(newRoot);
}

这奇怪地产生了以下没有nameof参数的代码修复建议(即使没有花括号):

我在这里失踪的是什么？

Answer 1

SeparatedSyntaxList<T>是不可改变的.
调用.Add()返回添加了令牌的新列表.

你忽略了这个新列表,所以你的令牌永远不会出现在任何地方.

你要

argsList = argsList.Add(SyntaxFactory.Argument(nameOfExp));