RestSharp with Async Await

RestSharp is an excellent open source project to use in a Windows Phone app if you want make http calls to a json api. However it doesn’t have any inbuilt support for the async await syntax. Thankfully with C#’s extensions methods we can add this support in our app.

namespace RestSharpEx
{
    public static class RestClientExtensions
    {
      public static Task<IRestResponse> ExecuteTaskAsync(this RestClient @this, RestRequest request)
      {
        if (@this == null)
            throw new NullReferenceException();
     
        var tcs = new TaskCompletionSource<IRestResponse>();
     
        @this.ExecuteAsync(request, (response) =>
        {
            if (response.ErrorException != null)
                tcs.TrySetException(response.ErrorException);
            else
                tcs.TrySetResult(response);
        });
     
        return tcs.Task;
      }
    }
}

This will add a new function to the RestSharp client type called ExecutreTaskAsync. Inside the method it will call the ExecuteAsync function as you normally would, but has also implemented returning a Task and setting it’s results when its complete.

To use the function would be as follows

var client = new RestClient("http://www.YOUR SITE.com/api/");
var request = new RestRequest("Products", Method.GET);
var response = await client.ExecuteTaskAsync(request);
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Convert string or int to enum

Enum’s a great, but you may be wondering how you can turn an integer or string value into the corresponding enum. For example you may have an api that’s being sent XML or JSON, and then you need to turn one of the values within that into an enum to set on an object in your code.

Well it’s very simple. If you have a string do this:

YourEnum foo = (YourEnum) Enum.Parse(typeof(YourEnum), yourString);

or if you have an int do this (you could also just do the first example with a ToString() on the end.

YourEnum foo = (YourEnum)yourInt;

Back to basics string vs StringBuilder

This is simple stuff but is something I see people easily miss by just not thinking about it.

A string is an immutable object, which means once created it can not be altered. So if you want to do a replace or append some more text to the end a new object will be created.

A StringBuilder however is a buffer of characters that can be altered without the need for a new object to be created.

In the majority of situations a string is a perfectly reasonable choice and creating an extra 1 or 2 objects when you appened a couple of other strings isn’t going to make a significant impact on the performance of your program. But what happens when you are using strings in a loop.

A few weeks ago one of my developers had written some code that went through a loop building up some text. It looked a little like this:

string foo = "";

foreach (string baa in someSortOfList)
{
    foo += " Value for " + baa + " is: ";

    var aValue = from x in anotherList
                 where x.name == baa
                 select x;

    foo += aValue.FirstOrDefault().value;
}

Everything worked apart from the fact it took 30seconds to execute!

He was searching through convinced that the linq expressions in the middle was what was taking the time, and was at the point of deciding it could not go any faster without a new approach.

I pointed out not only had he used strings rather than a StringBuilder, but the loop also created around 10 string objects within it. The loop which repeated a couple thousand times was therefore creating 20000 objects that weren’t needed. After we switched froms strings to a StringBuilders the loop executed in milliseconds.

So remember when your trying to work out why your code may be slow, remember the basic stuff.