ASP.NET Core API sending string wrapped in double quotes

Question

My ASP.NET Core API generates a SAS for a file to be uploaded to Azure Blob Storage. Looks like the string is being wrapped in double quotes and this is creating a problem with the front end solution I'm using to upload files.

How can I return a string but make sure that it's not wrapped in double quotes?

This is the API controller:

public async Task<IActionResult> GetSAS(string blobUri, string _method)
{
    if (string.IsNullOrEmpty(blobUri) || string.IsNullOrEmpty(_method))
       return new StatusCodeResult(400);

    // Get SAS
    var sas = _fileServices.GetSAS(blobUri, _method);

    return Ok(sas);
}

What does your controller method look like? ASP.NET core shouldn't wrap in double quotes by default but it sounds like your response is getting formatted as JSON somehow. — Pace, Dec 28 '17 at 15:18
Just posted the API method. At the top of my API controller, I do have `[Produces("application/json")]` which explains why it's a `JSON` — Sam, Dec 28 '17 at 15:21
@DavidG Yes, SAS is string but my API controller is producing JSON — Sam, Dec 28 '17 at 15:22
This is the only method that is supposed to return `string` in my controller. How can I override `[Produces("application/json")]` only for that method? — Sam, Dec 28 '17 at 15:22
Sorry, just corrected my typo. This method is the only one that is supposed to return `string`. All the others need to return `JSON`. So, I need to override this setting only for this particular method. — Sam, Dec 28 '17 at 15:23
Thank you! I needed to use `[Produces("text/plain")]`. Please post your comment as an answer so that I can accept it. Thanks again! — Sam, Dec 28 '17 at 15:31
Just remove ```[Produces("application/json")]```, see: https://stackoverflow.com/a/73806345/9258504 — SamBerk, Sep 21 '22 at 20:06

score 7 · Accepted Answer · answered Dec 28 '17 at 15:36

As discussed in the comments you have a [Produces] attribute on the class that is forcing a JSON response. From the docs on ProducesAttribute we can see it can be applied to an action as well as the controller. So, you can override for a particular action by adding it there, in your case you need text/plain:

[Produces("text/plain")]
public async Task<IActionResult> GetSAS(string blobUri, string _method)
{
    //snip
}

score 4 · Answer 2 · answered Dec 28 '17 at 15:42

4

You're returning an OkResult, which will serialize the object passed into it. Since that object is a string, and since the default serializer is JSON, your response ends up as a JSON string, i.e. with double quotes around it.

To fix this, you can take a number of different paths. First, you can simply change the return type to string. That will cause a ContentResult to be wrapped around it, which will not result in serialization. For example:

public async Task<string> GetSAS(string blobUri, string _method)
{
    ...

    return sas;
}

Second, you can use the Produces attribute to dictate the return content type as text/plain.

[Produces("text/plain")]
public async Task<IActionResult> GetSAS(string blobUri, string _method)

Lastly, you can simply leave it as-is, and instead interpret the result correctly as JSON on the client-side. You can use JSON.parse in your JavaScript code to get the string value:

var sas = JSON.parse(result);

answered Dec 28 '17 at 15:42

Chris Pratt

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Great explanation. Thank you! Because @DavidG spent time helping me, I picked his as the answer but at least wanted to thank you for the great explanation! – Sam Dec 28 '17 at 15:45
1

Sure. No problem. I figured as much. I just wanted to add the explanation and some alternative ways to solve the issue for posterity. – Chris Pratt Dec 28 '17 at 15:46
@Sam It's not about time, it's about the right answer - this one is clearly more detailed, I'd be happy if you switched it. – DavidG Dec 28 '17 at 15:48
I think I'll let the great people of SO and history decide :-) Thank you both very much! – Sam Dec 28 '17 at 15:50

ASP.NET Core API sending string wrapped in double quotes

2 Answers2