private async Task <Document> CreateFieldAsync(CodeRefactoringContext context, ParameterSyntax parameter,
string paramName, string fieldName, CancellationToken cancellationToken)
{
var oldConstructor = parameter.Ancestors().OfType <ConstructorDeclarationSyntax>().First();
var newConstructor = oldConstructor.WithBody(oldConstructor.Body.AddStatements(
SyntaxFactory.ExpressionStatement(
SyntaxFactory.AssignmentExpression(
SyntaxKind.SimpleAssignmentExpression,
SyntaxFactory.IdentifierName(fieldName),
SyntaxFactory.IdentifierName(paramName)))));
var oldClass = parameter.FirstAncestorOrSelf <ClassDeclarationSyntax>();
var oldClassWithNewCtor = oldClass.ReplaceNode(oldConstructor, newConstructor);
var fieldDeclaration = RoslynHelpers.CreateFieldDeclaration(RoslynHelpers.GetParameterType(parameter), fieldName);
var newClass = oldClassWithNewCtor
.WithMembers(oldClassWithNewCtor.Members.Insert(0, fieldDeclaration))
.WithAdditionalAnnotations(Formatter.Annotation);
var oldRoot = await context.Document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
var newRoot = oldRoot.ReplaceNode(oldClass, newClass);
return(context.Document.WithSyntaxRoot(newRoot));
}
