HttpClient asynchronous Post C#

Question

I have this line of code:

HttpResponseMessage aResponse = await aClient.PostAsync(theUri, theContent);

However, I have an error that says: The 'await' operator can only be used within an async method. Consider marking this method with the 'async' modifier and changing its return type to 'Task'.

So I went to search and found this link: Troubleshooting HTTPClient asynchronous POST and reading results

I've tried what the answer does, but I still get that error. What should I do? Thanks a million

Answer 1

You need to decorate the method containing the await call with async and wrap it's return type in Task<TResult> . For example, if you were calling it from an Index() action of a Controller in MVC, you would have to modify:

public ActionResult Index() 
{
    HttpResponseMessage aResponse = await aClient.PostAsync(theUri, theContent);
    //will give you the error you are getting
}

..so it becomes:

public async Task<ActionResult> Index() 
{
    HttpResponseMessage aResponse = await aClient.PostAsync(theUri, theContent);
    //no error here
}

Have a look at async (C# Reference) on MSDN.

There's also the case of returning Task when no meaningful value is returned and void , used primarily to define event handlers, which require that return type.

For all the possible return types of async methods, have a look at Async Return Types (C# and Visual Basic) on MSDN.

As an aside, these operations require referencing System.Threading.Tasks in your project.

Answer 2

Make sure that the method containing this line of code is marked async and returns a Task object.

http://msdn.microsoft.com/en-us/library/hh156513.aspx