Question 389007 in ASP.NET Question posted in
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Asp.net – How to read nullable string from httpResponseMessage

We have an api method that can return a null value. It returns its like this:

 var formattedValue= null;
 return Ok(formattedValue);

Then on the client we parse the response like this:

 // Check if it's null
 var result = await httpResponseMessage.Content.ReadAsStringAsync();
 if (result == null)
 {
     return null;
 }

however the ReadAsStringAsync() returns an empty string by default.

I can’t find a way to check if the content is completely empty ie null.

Tags:

2

Answers


  1. 0

    On the client side, you can use the following code to parse the response:

    // Check if it's null
var result = await httpResponseMessage.Content.ReadAsStringAsync();

if (string.IsNullOrEmpty(result))
{
    return null;
}

    In this case, ReadAsStringAsync() will return an empty string instead of null. To ensure the content is completely empty, i.e., null, you can use string.IsNullOrEmpty(result) to check.

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  2. 0

    There are Headers which are associated with the HttpResponseMessage

    • like Allow, Age, RetryAfter, etc.

    There are other Headers which are associated with the HttpContent

    • like Content-Range, Content-Length, Content-Type, etc.

    For more details please check this post.

    Gladly it is quite easy to fetch the Content-Length through the HttpContent:

    var httpClient = new HttpClient();
var response = await httpClient.GetAsync("https://postman-echo.com/time/now");
var length = response.Content.Headers.ContentLength; // 29, because the body is not empty

    var httpClient = new HttpClient();
var response = await httpClient.GetAsync("https://postman-echo.com/patch");
var length = response.Content.Headers.ContentLength; // 0, because the body is empty

    So, you can branch based on the ContentLength

    if (httpResponseMessage.Content.Headers.ContentLength > 0)
{
    ...
}
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