如何在Azure Functions OpenAPI扩展中添加只读属性？

方案1：直接用扩展包自带的[OpenApiReadOnly]属性 #

别慌，这个OpenApi扩展包其实已经支持只读属性的标注，只是你看的文档没明说。直接用Microsoft.Azure.WebJobs.Extensions.OpenApi.Attributes命名空间下的[OpenApiReadOnly]，效果和旧版[ReadOnly(true)]完全一致：

• 像POST、PUT这类写操作，标了这个属性的字段会自动从请求体里消失
• GET这类读操作，字段会正常显示在响应里

改完的模型示例：

using Microsoft.Azure.WebJobs.Extensions.OpenApi.Attributes;

public class ThingModel
{
    [Display(Name = "Thing Id", Description = "Thing Model Id")]
    [OpenApiReadOnly] // 替换原来的[ReadOnly(true)]
    public Guid? Id { get; set; }

    [Display(Name = "Thing Name", Description = "Name of Thing")]
    [OpenApiRequired] // 对应旧版的[Required(HttpMethodType.Post)]，扩展包会自动识别请求方法
    public string Name { get; set; }

    [Display(Name = "Thing Description", Description = "Description of Thing")]        
    public string Description { get; set; }
}

方案2：自定义筛选器（针对特殊场景） #

如果需要更细的控制——比如只在特定HTTP方法里隐藏字段，就自己写个Schema筛选器：

1. 先定义自定义属性：

[AttributeUsage(AttributeTargets.Property)]
public class ReadOnlyForHttpMethodAttribute : Attribute
{
    public HttpMethod[] ExcludedMethods { get; }

    public ReadOnlyForHttpMethodAttribute(params HttpMethod[] excludedMethods)
    {
        ExcludedMethods = excludedMethods;
    }
}

2. 实现筛选逻辑：

using Microsoft.OpenApi.Models;
using Microsoft.Azure.WebJobs.Extensions.OpenApi.Core.Abstractions;
using Microsoft.Azure.WebJobs.Extensions.OpenApi.Core.Extensions;

public class ReadOnlySchemaFilter : IOpenApiSchemaFilter
{
    public void Apply(OpenApiSchema schema, SchemaFilterContext context)
    {
        if (context.ApiOperation is null || schema.Properties is null)
            return;

        var httpMethod = new HttpMethod(context.ApiOperation.Method.ToString().ToUpper());

        var propertiesToRemove = context.Type.GetProperties()
            .Where(p => p.GetCustomAttribute<ReadOnlyForHttpMethodAttribute>() is { } attr && 
                        attr.ExcludedMethods.Contains(httpMethod))
            .Select(p => p.Name.ToCamelCase()) // 扩展包默认用驼峰命名，注意匹配
            .ToList();

        foreach (var prop in propertiesToRemove)
        {
            schema.Properties.Remove(prop);
        }
    }
}

3. 注册筛选器：

   • 要是用的隔离进程模型，在Program.cs里添加：

     var host = new HostBuilder()
         .ConfigureFunctionsWorkerDefaults()
         .ConfigureServices(services =>
         {
             services.AddOpenApiCore()
                 .AddSchemaFilter<ReadOnlySchemaFilter>();
         })
         .Build();
     
     host.Run();
     

   • 要是进程内模型，就在Startup.cs的ConfigureServices里添加：

     services.AddOpenApi()
         .AddSchemaFilter<ReadOnlySchemaFilter>();
     

4. 模型中使用自定义属性：

public class ThingModel
{
    [Display(Name = "Thing Id", Description = "Thing Model Id")]
    [ReadOnlyForHttpMethod(HttpMethod.Post, HttpMethod.Put)] // 只在POST/PUT操作里隐藏该字段
    public Guid? Id { get; set; }

    // 其他属性正常编写即可
}

额外提醒 #

• OpenApiRequired比旧版的Required属性省心，不用指定HTTP方法，它会自动根据请求类型判断是否标记为必填。

内容的提问来源于stack exchange，提问作者DDevs