Roslyn: how to multiple edit document in a CodeFixProvider

[wangshuai-007]

Analyzer package

Microsoft.CodeAnalysis.Analyzers

Package Version

v2.6.2

Repro steps

I create a CodeFixProvider to move Message.Show() text to another *.cs file
Now I can add the property to the current file;it looks like this:

follow this guid applying-multiple-changes-to-a-solution-in-roslyn,I try to use Workspace.TryApplyChanges(), but I got TryApplyChanges cannot be called from a background thread error ,then I know It is normal for fix this error Calling TryApplyChanges from a background thread explodes in hard-to-understand ways #17782

And Now,I want to know,is there a way to edit another *.cs file in a CodeFixProvider?
I wish the preview changes can show all the changes

Expected behavior

Actual behavior

[mavasani]

@vatsalyaagrawal can we port this issue to Roslyn repo?

[mavasani]

@w371987114 workspace.TryApplyChanges is not meant to be called from a CodeFixProvider. You instead want to use a SyntaxEditor, apply multiple edits using this editor and then invoke editor.GetChangedDocumentAsync() to get the new document with multiple edits.

[CyrusNajmabadi]

I think they want to edit multiple files. In which case, you should return a properly updated Solution from the code action instead of just updating a Document.

[mavasani]

Ah thanks @CyrusNajmabadi - I misread the question as multiple edits to the same document.

[wangshuai-007]

CyrusNajmabadi is right
So, is there a way to edit another Document in a CodeFixProvider?
and the Preview changes form can see all the changes of Document in the project

[sharwell]

@w371987114 When you register the code fix, have it return a Solution instead of a Document. The updated solution may contain changes to any number of documents. The automatic preview will only show the changes to the first document, but if you click Preview changes it will show all changes.

[wangshuai-007]

@w371987114 When you register the code fix, have it return a Solution instead of a Document. The updated solution may contain changes to any number of documents. The automatic preview will only show the changes to the first document, but if you click Preview changes it will show all changes.

sharwell gave me a right answer,CodeAction.Create has a overload method with Func<CancellationToken,Task<Solution>> parameter, It can register solution CodeFix.
my code is like this:
```c#
public class MyAnalyzerCodeFixProvider : CodeFixProvider
{
public sealed override async Task RegisterCodeFixesAsync(CodeFixContext context)
{
....
context.RegisterCodeFix(
CodeAction.Create(title, c =>
FixRegexAsync(context.Document, variableDeclare, c), equivalenceKey: title), diagnostic);

    }
    private async Task<Solution> FixRegexAsync(Document document,
        InvocationExpressionSyntax invocationExpr,
        CancellationToken cancellationToken)
    {
        ....
        var solution = document.Project.Solution;
        var cultureDocument =
            document.Project.Documents.FirstOrDefault(c => c.Name == "CultureMessageText.cs");
        if (cultureDocument == null) return document.Project.Solution;
        var cultureRoot = await cultureDocument?.GetSyntaxRootAsync();
        if (cultureRoot == null) return document.Project.Solution;
        ....
        solution = solution.WithDocumentSyntaxRoot(document.Id, newRoot);
        solution = solution.WithDocumentSyntaxRoot(cultureDocument.Id, cultureRoot);

        return solution;
    }

}
```