Roslyn：将 using 语句添加到语法树答案

【问题标题】：Roslyn: Add using statements to Syntax treeRoslyn：将 using 语句添加到语法树
【发布时间】：2020-08-28 03:31:05
【问题描述】：

我已经成功创建了一个代码修复程序，如果通用工厂类中缺少工厂方法，它会生成工厂方法。当我查看已修复的文件时，由于缺少 using 语句，我收到了许多错误。

我已经能够创建一个我想添加到重构文件中的 UsingDirectives 列表。如何将这些使用添加到文件中？

    private async Task<Solution> FixUpFactory(Document document, TypeDeclarationSyntax typeDecl, CancellationToken cancellationToken)
        {
...
var factorySyntaxTree = factoryClass.DeclaringSyntaxReferences.Select(x => x.SyntaxTree);
var factoryDocument = document.Project.GetDocument(factorySyntaxTree.FirstOrDefault());
var usingDirectives = FindUsingDirectives(factorySyntaxTree.FirstOrDefault());
var methodUsingDirectives = FindMethodUsingDirectives(createMethods);
var usingDirectivesToAdd = new SyntaxList<UsingDirectiveSyntax>(methodUsingDirectives.Except(usingDirectives).Distinct());
...
//replace 
var factoryTree = await factoryDocument.GetSyntaxTreeAsync();
var compUnitSyntax = factoryTree.GetCompilationUnitRoot();
var newCompUnitSyntax = compUnitSyntax.WithUsings(usingDirectivesToAdd);

var documentRoot = await factoryDocument.GetSyntaxRootAsync().ConfigureAwait(false);
//newRoot comes out the same as the documentRoot
var newRoot= documentRoot.ReplaceNode(compUnitSyntax, newCompUnitSyntax);
var factorySolution = document.Project.Solution.WithDocumentSyntaxRoot(factoryDocument.Id, newRoot);
}

那么，如何让 newRoot 反映我想添加的新 using 指令？

【问题讨论】：

标签： c# roslyn roslyn-code-analysis

【解决方案1】：

我最终打破了我的代码。这两种方法都有效：

private SyntaxTree UpdateUsingDirectives(SyntaxTree originalTree, UsingDirectiveSyntax[] newUsings)
{
    var rootNode = originalTree.GetRoot() as CompilationUnitSyntax;
    rootNode = rootNode.AddUsings(newUsings).NormalizeWhitespace();
    return rootNode.SyntaxTree;
}

private SyntaxTree UpdateUsingDirectives(SyntaxTree originalTree, SyntaxList<UsingDirectiveSyntax> newUsings)
{
    var rootNode = originalTree.GetRoot() as CompilationUnitSyntax;
    rootNode = rootNode.WithUsings(newUsings).NormalizeWhitespace();
    return rootNode.SyntaxTree;
}

注意第二个替换了 usings。

之后，您可以执行以下操作：

var newFactory = UpdateUsingDirectives(factoryTree, newUsings);
var newFactoryRoot = newFactory.GetRoot();

var documentRoot = await factoryDocument.GetSyntaxRootAsync().ConfigureAwait(false);

var newRoot= documentRoot.ReplaceNode(document.getRoot(), newFactoryRoot);
var factorySolution = document.Project.Solution.WithDocumentSyntaxRoot(factoryDocument.Id, newRoot);

【讨论】：