How to make a route parameter optional in Azure Function

Question

public static async Task<HttpResponseMessage> Run([HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = "ResolveKey/{key}/{resolver}")]HttpRequestMessage req, TraceWriter log, string key,string resolver= "default")

In the above code I tried to make resolver parameter optional by setting a default value string resolver= "default" . The code compiles and runs fine, but the URL always wants resolver parameter to be present, otherwise I get 404.

I want to make the resolver parameter optional in the above code. Is there any way?

score 42 · Accepted Answer · answered Jun 16 '17 at 17:20

42

You can express that a parameter is optional in the route template itself.

For the route above, you can just change your template to the following:

ResolveKey/{key}/{resolver?}

You can find more information about optional routes and default values here

answered Jun 16 '17 at 17:20

Fabio Cavalcante

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For those who are looking to match a full path in the resolver, Azure function will url encode the `{resolver?}` match by default. You will need to include an app setting to work around this, `AZURE_FUNCTION_PROXY_BACKEND_URL_DECODE_SLASHES : true`. (https://github.com/Azure/azure-functions-host/issues/2249#issuecomment-391167871) – James Aug 30 '20 at 19:42

score 3 · Answer 2 · answered Jan 31 '18 at 13:49

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Azure Functions now support regular expressions. You can change your routing template to

ResolveKey/{key}/{*resolver}

answered Jan 31 '18 at 13:49

Eelco Koster

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score 1 · Answer 3 · answered Apr 13 '23 at 14:28

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The previous answers helped me out but I would have spent even less time if I had seen an example. Here I provide you one:

answered Apr 13 '23 at 14:28

Luis Gouveia

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How to make a route parameter optional in Azure Function

3 Answers3