使用Roslyn向类添加新的字段声明

using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;

public class FieldAdder : CSharpSyntaxRewriter
{
    public override SyntaxNode VisitClassDeclaration(ClassDeclarationSyntax node)
    {
        // 判断是否为目标类
        if (node.Identifier.ValueText == "TargetClass")
        {
            // 创建新的字段声明节点
            var fieldDeclaration = SyntaxFactory.FieldDeclaration(
                SyntaxFactory.VariableDeclaration(
                    SyntaxFactory.ParseTypeName("int"),
                    SyntaxFactory.SingletonSeparatedList(
                        SyntaxFactory.VariableDeclarator(
                            SyntaxFactory.Identifier("newField")
                        )
                    )
                )
            )
            .WithModifiers(SyntaxFactory.TokenList(SyntaxFactory.Token(SyntaxKind.PrivateKeyword)));

            // 将新的字段声明节点添加到目标类节点的成员列表中
            var newMembers = node.Members.Add(fieldDeclaration);

            // 更新目标类节点
            return node.WithMembers(newMembers);
        }

        return base.VisitClassDeclaration(node);
    }
}

public class Program
{
    public static void Main()
    {
        // 解析源代码为语法树
        var syntaxTree = CSharpSyntaxTree.ParseText(@"
            using System;

            public class TargetClass
            {
                public void Method()
                {
                    Console.WriteLine(""Hello, World!"");
                }
            }
        ");

        // 获取根节点
        var root = syntaxTree.GetRoot();

        // 创建字段添加器
        var fieldAdder = new FieldAdder();

        // 修改语法树
        var newRoot = fieldAdder.Visit(root);

        // 生成修改后的源代码
        var newSourceCode = newRoot.ToFullString();

        Console.WriteLine(newSourceCode);
    }
}