Adding custom attributes to C# classes using Roslyn

Question

Consider the following class in a file \"MyClass.cs\"

using System;

public class MyClass : Entity
{
    public long Id
    {
        get;
               


        

Answer 1

One of the parameters of the Syntax.PropertyDeclaration method is a list of attributes that apply to the attribute. Like all Syntax elements, it is constructed using a factory method on the static SyntaxFactory class.

The Roslyn Quoter can be handy for figuring out how to generate syntax using Roslyn.

In your particular example, the VisitPropertyDeclaration method of your rewriter should look something like:

using static Microsoft.CodeAnalysis.CSharp.SyntaxFactory;
...

    protected override SyntaxNode VisitPropertyDeclaration(PropertyDeclarationSyntax node)
{
    var typeSyntax = node.Type;

    if (node.Identifier.ValueText == "Id")
    {
        typeSyntax = SyntaxFactory.IdentifierName("string");
    }

    var newProperty = PropertyDeclaration(
                PredefinedType(
                    Token(SyntaxKind.LongKeyword)),
                Identifier("Id"))
            .WithModifiers(
                TokenList(
                    Token(SyntaxKind.PublicKeyword)))
            .WithAccessorList(
                AccessorList(
                    List(new AccessorDeclarationSyntax[]{
                        AccessorDeclaration(
                            SyntaxKind.GetAccessorDeclaration)
                        .WithSemicolonToken(
                            Token(SyntaxKind.SemicolonToken)),
                        AccessorDeclaration(
                            SyntaxKind.SetAccessorDeclaration)
                        .WithSemicolonToken(
                            Token(SyntaxKind.SemicolonToken))})))
            .NormalizeWhitespace();

    return newProperty;
}