将 C# 代码与 roslyn 合并：注释消失

Question

场景：我正在尝试使用 Roslyn 将一组 C# 源代码片段合并为一个代码片段。

问题：解析带有前导注释的不同类时，第一个类（SomeClass在示例中）上方的注释不会保留。对于第二个类 ( AnotherClass)，注释被保留...

下面的代码演示了这个问题。在控制台程序中使用它（并安装 Microsoft.CodeAnalysis.CSharp nuget 包）

using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using System.Collections.Generic;
using System.Diagnostics;
using System;

namespace roslyn01
{
    class Program
    {
        static void Main(string[] args)
        {
            var input = new[]
            {
               "// some comment\r\nclass SomeClass {}",
               "// another comment\r\nclass AnotherClass {}",
            };

            // parse all input and collect members
            var members = new List<MemberDeclarationSyntax>();
            foreach (var item in input)
            {
                var syntaxTree = CSharpSyntaxTree.ParseText(item);
                var compilationUnit = (CompilationUnitSyntax)syntaxTree.GetRoot();
                members.AddRange(compilationUnit.Members);
            }

            // assemble all members in a new compilation unit
            var result = SyntaxFactory.CompilationUnit()
                .AddMembers(members.ToArray())
                .NormalizeWhitespace()
                .ToString();

            var expected = @"// some comment
class SomeClass
{
}

// another comment
class AnotherClass
{
}";

            Console.WriteLine(result);
            // the assert fails; the first comment ('// some comment') is missing from the output
            Debug.Assert(expected == result);
        }
    }
}

我错过了什么？

Answer 1

您正在使用ToString()而不是ToFullString()转换CompilationUnitSyntax为string. ToString()返回一个删除前导和尾随琐事（包括注释）的字符串，但ToFullString()不会删除此琐事。你可以在代码文档中看到：

//
// Description:
//     Returns the string representation of this node, not including its leading and
//     trailing trivia.
//
// Returns:
//     The string representation of this node, not including its leading and trailing
//     trivia.
//
// Comments:
//     The length of the returned string is always the same as Span.Length
public override string ToString();

//
// Description:
//     Returns full string representation of this node including its leading and trailing
//     trivia.
//
// Returns:
//     The full string representation of this node including its leading and trailing
//     trivia.
//
// Comments:
//     The length of the returned string is always the same as FullSpan.Length
public virtual string ToFullString();