Modify Request.Content in WebApi DelegatingHandler - asp.net-web-api

Question

I need to modify requested content to replace some characters (because of some unicode problems). Previously (in ASP.NET MVC), I did this with HttpModules; but in WebApi, it seems that I should DelegatingHandler but it is totally different.
How can I modify request.Content inside the SendAsync method? I need something like this:
protected async override Task<HttpResponseMessage> SendAsync(
HttpRequestMessage request, CancellationToken cancellationToken)
{
var s = await request.Content.ReadAsStringAsync();
// do some modification on "s"
s= s.replace("x","y");
request.Content = new StringContent(s);
var response = await base.SendAsync(request, cancellationToken);
return response;
}
In the code above, I think I should check the request's content type and then decide what to do. If yes, which checks should I do?

Answer 1

I did something like this in SendAsync. Although it is not a comprehensive solution, it works:
//first : correct the URI (querysting data) first
request.RequestUri = new Uri(Correcr(request.RequestUri.ToString()));
var contentType = request.Content.Headers.ContentType;
if (contentType != null)
{
if (contentType.MediaType == "application/x-www-form-urlencoded")//post,put,... & other non-json requests
{
var formData = await request.Content.ReadAsFormDataAsync();
request.Content = new FormUrlEncodedContent(Correct(formData));
}
else if (contentType.MediaType == "multipart/form-data")//file upload , so ignre it
{
var formData = await request.Content.ReadAsFormDataAsync();
request.Content = new FormUrlEncodedContent(Correct(formData));
}
else if (contentType.MediaType == "application/json")//json request
{
var oldHeaders = request.Content.Headers;
var formData = await request.Content.ReadAsStringAsync();
request.Content = new StringContent(Correct(formData));
ReplaceHeaders(request.Content.Headers, oldHeaders);
}
else
throw new Exception("Implement It!");
}
return await base.SendAsync(request, cancellationToken);
and this helper function:
private void ReplaceHeaders(HttpContentHeaders currentHeaders, HttpContentHeaders oldHeaders)
{
currentHeaders.Clear();
foreach (var item in oldHeaders)
currentHeaders.Add(item.Key, item.Value);
}