Windows.Web.Http.HttpClient post send special characters (A potentially dangerous Request.Form value was detected from the client)

Question

I need to send the following text to a web application (MVC2)

Hello <>~!@#$%^&*()_+|}{":?><

Hello <>?:"P{{}|+)_)_&*()&^*^%&#%^@#$~!@#~!@#~Q

I'm sending this by a UWP app using Windows.Web.Http.HttpClient. However, when this message received from the web it throws an exception.

"A potentially dangerous Request.Form value was detected from the client (data="..._&*()&^*^%&#%^@#$~!@#~!@#~Q")."

The same message can be sent by Android and iOS apps and web server accepts it with no issue. Can someone help me to solve this without any server-side modification?

Here is the code I used on UWP app. Please let me know if need any alteration in here. Thanks again.

var httpBaseProtocolFilter = new HttpBaseProtocolFilter();
    httpBaseProtocolFilter.MaxVersion = HttpVersion.Http20;
    HttpClient httpClient = new HttpClient(httpBaseProtocolFilter);
    var requestUrl = Global.ServerUrl;

    httpClient = SetHeaders(httpClient);

    httpClient.DefaultRequestHeaders.Accept.Add(new HttpMediaTypeWithQualityHeaderValue("application/x-www-form-urlencoded"));
    HttpResponseMessage response = null;

    if (requestMehtod == ApplicationConstants.RequestType.POST) //Request type POST
    {
        if (postData != null && postData.Count > 0)
        {
            Dictionary<string, string> pairs = new Dictionary<string, string>();
            foreach (var item in postData)
            {
                val = (String.IsNullOrWhiteSpace(item.Value)) ? "" : item.Value;
                pairs.Add(item.Key, val);
            }

            Uri uri = new Uri(requestUrl);
            HttpFormUrlEncodedContent formContent = new HttpFormUrlEncodedContent(pairs);
            response = await httpClient.PostAsync(uri, formContent).AsTask(cts.Token);
        }
    }

    responseText = await response.Content.ReadAsStringAsync();