Unable to translate bytes [FC] at index 35 from specified code page to Unicode
<p>I'm trying to send an object like this to my REST API(built with asp net core)</p>

<pre><code>{
    "firstName":"tersü",
    "lastName":"asda"
}
</code></pre>

<p>And this is how the headers form SoapUI look:</p>

<pre><code> Accept-Encoding: gzip,deflate
Content-Type: application/json:charset=UTF-16
Host: localhost:4004
Connection: Keep-Alive
User-Agent: Apache-HttpClient/4.1.1 (java 1.5)
</code></pre>

<p>However, my <code>actionContext.ModelState</code> is always invalid because it can not work with the umlaute. The exception is the following:</p>

<blockquote>
  <p>Unable to translate bytes [FC] at index 35 from specified code page to
  Unicode</p>
</blockquote>

<p>If it's any help, the method signature looks like this: </p>

<pre><code>[ValidateUserData]
public async Task&lt;IActionResult&gt; Update(string userId, [FromBody] UpdateUserRequest updateRequest)
</code></pre>

<p>Basically the code never goes over    </p>

<pre><code>if (!actionContext.ModelState.IsValid)
{
    actionContext.Result = new BadRequestObjectResult(actionContext.ModelState);
}
</code></pre>

<p>inside the <code>[ValidateUserData]</code> attribute</p>

<p>What am I missing here?</p>