How can I check to see if an http request has no query strings in ASP.Net Core web API

Question

I am working on an ASP.Net Core web API using REST verbs with optional query string parameters.

For example, the API call looks like this;

http://localhost:5010/servicetypecode?stc=123

or http://localhost:5010/servicetypecode?mailclasscode=fc

I am using code like this to set up the query strings

    public IActionResult Get([FromQuery] string mailclasscode, [FromQuery] string stc) { ... }

So, in my method body, I am evaluating each string individually like this...

    if (!string.IsNullOrEmpty(mailclasscode)) { ... }


    if (!string.IsNullOrEmpty(stc)) { ... }

However, I would like to allow my users to just make a straight up GET to the API with no query string parameters provided and return a list of all records, unfiltered.

So a call like this;

http://localhost:5010/servicetypecode

But I would prefer not to have to do this in my method body, especially if I were to have a lot of query string parameters;

if (string.IsNullOrEmpty(mailclasscode) && string.IsNullOrEmpty(stc)) { ... }

Is there a way to simply determine if no query string parameters were provided without evaluating every possible query string parameter?

Also, is there a better way to evaluate query string parameters than testing every possible parameter, in the case where I were to pass a lot of different query string parameters?

Thanks in advance for any help you can provide.

Alex Terry · Accepted Answer · 2017-07-08 17:43:34Z

2

You can check the incoming request.

if (this.HttpContext.Request.QueryString.HasValue)

Also as a note, if you have a lot of query string parameters, you can use a single class instead of multiple parameters in the method signature.

answered Jul 8, 2017 at 17:43

Alex Terry

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2 Comments

EiEiGuy Over a year ago

ATerry, thanks. This worked perfectly. The other part of the question I was asking was more about a better way of processing multiple query string parameters than just using multiple if statements within the body of the method (whether I am using multiple query strings or a class in the method signature). I am trying to use a single GET method but provide multiple filtering options so, currently, I am testing for each possible query string parameter using multiple if statements. This works but looks a bit cluttered.

Alex Terry Over a year ago

If you looking to do more of a query based api, almost like a data access api, you can make use of IQueryable with a limited or full implementation of OData. Also, you can look at GraphQL. These are both frameworks that will take your returned IQueryable and apply the necessary filters.

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