codeFixProvider.md

Multiple Diagnostic Code Fix Provider

The MutlipleDiagnosticCodeFixProvider type provides a generalized implementation that provides code fixes for multiple diagnostics reported on the same node, with specified fixable diagnostic IDs provided from DiagnosticDescriptor instances instead of their raw IDs.

Additionally, a code fix title is attempted to be retrieved from a ResourceManager.

Declaring Code Fix Provider

The FixableDiagnosticDescriptors can be easily initialized as an array of DiagnosticDescriptor instances retrieved from a relative diagnostic descriptor storage.

The code fix title is expected to be a resource with the name {TypeName}_Title. The CodeFixTitle property is overridable in the case that the resource is to be alternatively retrieved.

For example, a code fix provider named SomeCodeFixProvider, its code fix title would be the value of the resource named SomeCodeFixProvider_Title.

The fix all provider defaults to the WellKnownFixAllProviders.BatchFixer implementation, and is overridable.

The PerformCodeFixActionAsync method is the core of the implementation of a code fix, which will be executed on every diagnostic instance.

The resulting code fix class should have a structure similar to this:

[Shared]
[ExportCodeFixProvider(LanguageNames.CSharp, Name = nameof(ExampleRemover))]
public sealed class ExampleRemover : MultipleDiagnosticCodeFixProvider
{
    protected override IEnumerable<DiagnosticDescriptor> FixableDiagnosticDescriptors => new DiagnosticDescriptor[]
    {
        MOCKDiagnosticDescriptorStorage.Instance[0001]
    };

    protected sealed override ResourceManager ResourceManager => CodeFixResources.ResourceManager;

    protected override async Task<Document> PerformCodeFixActionAsync(CodeFixContext context, SyntaxNode syntaxNode, CancellationToken cancellationToken)
    {
        // adjust the document accordingly
    }
}