使用Roslyn将自定义属性添加到C＃类 [英] Adding custom attributes to C# classes using Roslyn

问题描述

使用系统将以下类考虑在文件 MyClass.cs中

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

using System;

public class MyClass : Entity<long>
{
    public long Id
    {
        get;
        set;
    }

    [Required]
    public string Name
    {
        get;
        set;
    }

    public string Slug
    {
        get;
        set;
    }

    public DateTime CreatedOn
    {
        get;
        private set;
    }

    public DateTime UpdatedOn
    {
        get;
        private set;
    }

    /* ... */
}

当前，我手动创建数据合同类，如下所示：

Currently I manually create data contract classes looking as follows:

[DataContract(Namespace = "http://example.com/", Name = "MyClass")]
public sealed class MyClass
{
    [DataMember(EmitDefaultValue = false, Name = "Id")]
    public long Id
    {
        get;
        set;
    }

    [DataMember(EmitDefaultValue = false, Name = "Name", IsRequired = true)]
    public string Name
    {
        get;
        set;
    }

    [DataMember(EmitDefaultValue = false, Name = "Slug")]
    public string Slug
    {
        get;
        set;
    }

    [DataMember(EmitDefaultValue = false, Name = "CreatedOn")]
    public DateTime CreatedOn
    {
        get;
        set;
    }

    [DataMember(EmitDefaultValue = false, Name = "UpdatedOn")]
    public DateTime UpdatedOn
    {
        get;
        set;
    }
}

我想使用Roslyn重写 MyClass .cs，因此它看起来就像我手动创建的类。当前我有以下内容：

I'd like to use Roslyn to rewrite "MyClass.cs" so its looks like the class I create by hand. Currently I have the following:

using System;
using System.IO;
using Roslyn.Compilers.CSharp;

internal class Program
{
    private static void Main()
    {
        var reader = new StreamReader(@"..\..\MyClass.cs");
        var source = reader.ReadToEnd();
        var tree = SyntaxTree.ParseCompilationUnit(source);
        var rewriter = new MyRewriter();
        var newRoot = rewriter.Visit(tree.Root);
        Console.WriteLine(newRoot.Format());
    }
}

public class MyRewriter : SyntaxRewriter
{
    protected override SyntaxNode VisitClassDeclaration(ClassDeclarationSyntax node)
    {
        var declaration = (TypeDeclarationSyntax) base.VisitClassDeclaration(node);

        return ((ClassDeclarationSyntax) declaration).Update(
            declaration.Attributes,
            Syntax.TokenList(Syntax.Token(SyntaxKind.PublicKeyword), Syntax.Token(SyntaxKind.SealedKeyword)),
            declaration.Keyword,
            declaration.Identifier,
            declaration.TypeParameterListOpt,
            null,
            declaration.ConstraintClauses,
            declaration.OpenBraceToken,
            declaration.Members,
            declaration.CloseBraceToken,
            declaration.SemicolonTokenOpt);
    }

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

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

        var newProperty = Syntax.PropertyDeclaration(
            modifiers: Syntax.TokenList(Syntax.Token(SyntaxKind.PublicKeyword)),
            type: typeSyntax,
            identifier: node.Identifier,
            accessorList: Syntax.AccessorList(
                accessors: Syntax.List(
                    Syntax.AccessorDeclaration(SyntaxKind.GetAccessorDeclaration, 
                    semicolonTokenOpt: Syntax.Token(SyntaxKind.SemicolonToken)),
                    Syntax.AccessorDeclaration(SyntaxKind.SetAccessorDeclaration,
                    semicolonTokenOpt: Syntax.Token(SyntaxKind.SemicolonToken))
                    )
                )
            );

        return newProperty;
    }
}

我一直在试图找到一种方法来添加DataMember和DataContract自定义属性为MyClass，但是没有成功。一个如何添加自定义属性？

I have been trying to find a way to add the DataMember and DataContract custom attributes to MyClass but have been unsuccessful. How does one add the custom attributes?

推荐答案

Syntax.PropertyDeclaration 的参数之一code>方法是适用于该属性的属性列表。像所有 Syntax 元素一样，它是在静态 SyntaxFactory 类上使用工厂方法构造的。

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.

Roslyn Quoter 可以很方便地弄清楚如何使用Roslyn生成语法

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

在您的特定示例中，重写器的 VisitPropertyDeclaration 方法应类似于：

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;
}       

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