如何通过CosmosDBInput绑定从ClaimsPrincipal获取参数查询CosmosDB？

问题原因 #

默认的CosmosDBInput绑定表达式仅能识别框架内置的变量（如HttpContext.User、请求参数等），无法直接访问你存储在FunctionContext.Features中的自定义ClaimsPrincipal实例，因此你尝试的模板语法无法生效。

方案1：将ClaimsPrincipal注入HttpContext，复用默认绑定表达式 #

如果可以修改认证中间件，只需将ClaimsPrincipal赋值给请求关联的HttpContext.User，即可使用默认绑定表达式：

1. 修改认证中间件，在存入Features的同时添加：

// 假设已获取到目标claimsPrincipal实例
var httpContextFeature = req.FunctionContext.Features.Get<IHttpContextFeature>();
if (httpContextFeature != null)
{
    httpContextFeature.HttpContext.User = claimsPrincipal;
}

2. 修改CosmosDBInput属性，使用默认表达式提取用户ID：

[CosmosDBInput(
    databaseName: "%CosmosDb%",
    containerName: "%CosmosContainer%",
    Connection = "CosmosDBConnection",
    SqlQuery = "SELECT TOP 1 * FROM area a WHERE a.objectId = {User.FindFirstValue('http://schemas.xmlsoap.org/ws/2005/05/identity/claims/nameidentifier')}")] 
List<Model> areas

注意：直接写入ClaimTypes.NameIdentifier的字符串值，避免编译时常量解析问题；绑定表达式用单引号包裹Claim类型字符串。

方案2：自定义绑定复用CosmosDBInput现有逻辑 #

若无法修改中间件，可通过自定义绑定扩展CosmosDBInput功能，无需从零开发：

步骤1：定义自定义属性（复用原有配置） #

创建继承自CosmosDBInputAttribute的自定义属性，保留所有原生配置项：

using Microsoft.Azure.WebJobs;

public class CosmosDBInputWithClaimsAttribute : CosmosDBInputAttribute
{
    public CosmosDBInputWithClaimsAttribute(string databaseName, string containerName) 
        : base(databaseName, containerName)
    {
    }
}

步骤2：实现自定义绑定提供者 #

重写CosmosDB绑定逻辑，添加从Features提取ClaimsPrincipal的逻辑：

using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Host.Bindings;
using Microsoft.Extensions.Options;
using Microsoft.Extensions.Logging;
using System.Linq;
using System.Security.Claims;

public class CustomCosmosDBBindingProvider : CosmosDBBindingProvider
{
    public CustomCosmosDBBindingProvider(IOptions<CosmosDBOptions> options, INameResolver nameResolver, ILoggerFactory loggerFactory) 
        : base(options, nameResolver, loggerFactory)
    {
    }

    public override async Task<IBinding> TryCreateAsync(BindingProviderContext context)
    {
        var customAttr = context.Parameter.GetCustomAttribute<CosmosDBInputWithClaimsAttribute>();
        if (customAttr != null)
        {
            var originalBinding = await base.TryCreateAsync(context);
            if (originalBinding != null)
            {
                return new CustomCosmosDBBinding(originalBinding, context.FunctionContext);
            }
        }
        return await base.TryCreateAsync(context);
    }
}

public class CustomCosmosDBBinding : IBinding
{
    private readonly IBinding _originalBinding;
    private readonly FunctionContext _functionContext;

    public CustomCosmosDBBinding(IBinding originalBinding, FunctionContext functionContext)
    {
        _originalBinding = originalBinding;
        _functionContext = functionContext;
    }

    public async Task<IValueProvider> BindAsync(BindingContext context)
    {
        // 从Features中提取自定义ClaimsPrincipal持有者（替换为你的实际Feature类型）
        var claimsHolder = _functionContext.Features.First(f => f is IClaimsPrincipalHolder);
        var userId = claimsHolder.ClaimsPrincipal.FindFirstValue(ClaimTypes.NameIdentifier);

        // 替换查询中的占位符
        var cosmosAttr = context.Parameter.GetCustomAttribute<CosmosDBInputWithClaimsAttribute>();
        if (!string.IsNullOrEmpty(cosmosAttr.SqlQuery))
        {
            cosmosAttr.SqlQuery = cosmosAttr.SqlQuery.Replace("{UserId}", $"\"{userId}\"");
        }

        return await _originalBinding.BindAsync(context);
    }

    public bool FromAttribute => _originalBinding.FromAttribute;
}

// 你的Feature需实现此接口（替换为实际定义）
public interface IClaimsPrincipalHolder
{
    ClaimsPrincipal ClaimsPrincipal { get; }
}

步骤3：注册自定义绑定提供者 #

在FunctionStartup中替换默认的CosmosDB绑定提供者：

using Microsoft.Azure.Functions.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection;

[assembly: FunctionsStartup(typeof(YourNamespace.Startup))]
namespace YourNamespace
{
    public class Startup : FunctionsStartup
    {
        public override void Configure(IFunctionsHostBuilder builder)
        {
            builder.Services.Replace(ServiceDescriptor.Singleton<IBindingProvider, CustomCosmosDBBindingProvider>());
        }
    }
}

步骤4：在函数中使用自定义属性 #

public async Task<HttpResponseData> Run(
    [HttpTrigger(AuthorizationLevel.Function, "get", Route = "area")] HttpRequestData req,
    [CosmosDBInputWithClaims(
        databaseName: "%CosmosDb%",
        containerName: "%CosmosContainer%",
        Connection = "CosmosDBConnection",
        SqlQuery = "SELECT TOP 1 * FROM area a WHERE a.objectId = {UserId}")] List<Model> areas)
{
    // 业务逻辑实现
}

内容的提问来源于stack exchange，提问作者Unnamed