Azure Function: use parameter for SqlQuery from ClaimsPrincipal

Question

I store ClaimsPrincipal inside FunctionContext.IInvocationFeatures list (inside auth middleware) and want to take a userId (key: ClaimTypes.NameIdentifier) as an argument to cosmosDb query. I can do it inside a function with this pseudo code:

 var allFeatures = ((HttpRequestData)req).FunctionContext.Features;
 var claimsPrincipalHolderFeature = allFeatures.First(..);
 var id = claimsPrincipalHolderFeature.Claims.First(c =>
     c.Type.Equals(ClaimTypes.NameIdentifier, StringComparison.OrdinalIgnoreCase)
 ).Value;
 // steps with CosmosClient

But I want to do it via CosmosDbInput attribute, something like:

public async Task<HttpResponseData> Run(
    [HttpTrigger(AuthorizationLevel.Function, "get", Route = "area")] HttpRequestData req,
    [CosmosDBInput(
        databaseName: "%CosmosDb%",
        containerName: "%CosmosContainer%",
        Connection = "CosmosDBConnection",
        SqlQuery = $"SELECT TOP 1 * FROM area a WHERE a.objectId = {{ClaimsPrincipal.Claims[{ClaimTypes.NameIdentifier}]}}")] List<Model> areas)

unfortunatelly this template{ClaimsPrincipal.Claims[{ClaimTypes.NameIdentifier}]} doesn't work, does anyone have any suggestions? If it's not possible and I need to implement custom bindings, it would be good to reuse some already existed code (CosmosDBInputAttribute and related code) and not create anything from scratch like for example described here

Answer 1

Bindings can use Expressions coming from other Bindings, for example, you can use something from the HttpTrigger into the CosmosDBInput, but from the environment, I see no documentation stating that it's possible.

Values can be bound from:

• App settings
• Trigger file name
• Trigger metadata
• JSON payloads (for example what is coming from the HttpTrigger)
• New GUID
• Current date and time

Reference: https://learn.microsoft.com/azure/azure-functions/functions-bindings-expressions-patterns