Did you know that the .NET compiler turns our async methods into classes? And that .NET adds a try/catch block to each of these classes, potentially hiding thrown exceptions? It's true! In this session, we will learn how to best use async/await in C# by analyzing how .NET compiles our async code. Join me as we take an existing app and optimize its async code together, showing off performance gains, better exception handling, improved run-time speed, smaller app size and more using the latest tools in C#12 + .NET 8!

1. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/

2. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/
ReadDataFromUrl
async Task ReadDataFromUrl(string url)
{
WebClient wc = new WebClient();
byte[] result = await wc.DownloadDataTaskAsync(url);
string data = Encoding.ASCII.GetString(result);
LoadData(data);
}

3. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/
ReadDataFromUrl
async Task ReadDataFromUrl(string url)
{
WebClient wc = new WebClient();
byte[] result = await wc.DownloadDataTaskAsync(url);
string data = Encoding.ASCII.GetString(result);
LoadData(data);
}
Thread 1

4. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/
ReadDataFromUrl
async Task ReadDataFromUrl(string url)
{
WebClient wc = new WebClient();
byte[] result = await wc.DownloadDataTaskAsync(url);
string data = Encoding.ASCII.GetString(result);
LoadData(data);
}
Thread 2*
*Can be any thread other than Thread 1
e.g. Thread 32

5. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/
ReadDataFromUrl
async Task ReadDataFromUrl(string url)
{
WebClient wc = new WebClient();
byte[] result = await wc.DownloadDataTaskAsync(url);
string data = Encoding.ASCII.GetString(result);
LoadData(data);
}
Thread 1

6. Compiler
Generated
Code

7. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/
async Task ReadDataFromUrl(string url)
{
WebClient wc = new WebClient();
byte[] result = await wc.DownloadDataTaskAsync(url);
string data = Encoding.ASCII.GetString(result);
LoadData(data);
}
ReadDataFromUrl

8. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/
async Task ReadDataFromUrl(string url)
{
WebClient wc = new WebClient();
byte[] result = await wc.DownloadDataTaskAsync(url);
string data = Encoding.ASCII.GetString(result);
LoadData(data);
}
ReadDataFromUrl
private sealed class <ReadDataFromUrl>d_1 : IAsyncStateMachine

9. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/
async Task ReadDataFromUrl(string url)
{
WebClient wc = new WebClient();
byte[] result = await wc.DownloadDataTaskAsync(url);
string data = Encoding.ASCII.GetString(result);
LoadData(data);
}
ReadDataFromUrl
private string <data>5_3;
private byte[] <result>5_2;
private WebClient <wc>5_1;
public string url;

10. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/
async Task ReadDataFromUrl(string url)
{
WebClient wc = new WebClient();
byte[] result = await wc.DownloadDataTaskAsync(url);
string data = Encoding.ASCII.GetString(result);
LoadData(data);
}
ReadDataFromUrl
private void MoveNext();

11. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/
ReadDataFromUrl_MoveNext
public void MoveNext()
{
uint num = (uint)this.$PC;
this.$PC = -1;
try {
switch (num) {
case 0:
this.<wc>__0 = new WebClient();
this.$awaiter0 = this.<wc>__0.DownloadDataTaskAsync(this.url).GetAwaiter();
this.$PC = 1;
...
return;
break;
case 1:
this.<result>__1 = this.$awaiter0.GetResult();
this.<data>__2 = Encoding.ASCII.GetString(this.<result>__1);
this.$this.LoadData(this.<data>__2);
break;
default:
return;
}
}
catch (Exception exception) { ... }
this.$PC = -1;
this.$builder.SetResult();
}

12. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/
public void MoveNext()
{
uint num = (uint)this.$PC;
this.$PC = -1;
try {
switch (num) {
case 0:
this.<wc>__0 = new WebClient();
this.$awaiter0 = this.<wc>__0.DownloadDataTaskAsync(this.url).GetAwaiter();
this.$PC = 1;
...
return;
break;
case 1:
this.<result>__1 = this.$awaiter0.GetResult();
this.<data>__2 = Encoding.ASCII.GetString(this.<result>__1);
this.$this.LoadData(this.<data>__2);
break;
default:
return;
}
}
catch (Exception exception) { ... }
this.$PC = -1;
this.$builder.SetResult();
}
ReadDataFromUrl_MoveNext
case 0:
this.<wc>__0 = new WebClient();
this.$awaiter0 = this.<wc>__0.DownloadDataTaskAsync(this.url).GetAwaiter();
this.$PC = 1;
...
return;

13. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/
public void MoveNext()
{
uint num = (uint)this.$PC;
this.$PC = -1;
try {
switch (num) {
case 0:
this.<wc>__0 = new WebClient();
this.$awaiter0 = this.<wc>__0.DownloadDataTaskAsync(this.url).GetAwaiter();
this.$PC = 1;
...
return;
break;
case 1:
this.<result>__1 = this.$awaiter0.GetResult();
this.<data>__2 = Encoding.ASCII.GetString(this.<result>__1);
this.$this.LoadData(this.<data>__2);
break;
default:
return;
}
}
catch (Exception exception) { ... }
this.$PC = -1;
this.$builder.SetResult();
}
ReadDataFromUrl_MoveNext
case 1:
this.<result>__1 = this.$awaiter0.GetResult();
this.<data>__2 = Encoding.ASCII.GetString(this.<result>__1);
this.$this.LoadData(this.<data>__2);
break;

14. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/
public void MoveNext()
{
uint num = (uint)this.$PC;
this.$PC = -1;
try {
switch (num) {
case 0:
this.<wc>__0 = new WebClient();
this.$awaiter0 = this.<wc>__0.DownloadDataTaskAsync(this.url).GetAwaiter();
this.$PC = 1;
...
return;
break;
case 1:
this.<result>__1 = this.$awaiter0.GetResult();
this.<data>__2 = Encoding.ASCII.GetString(this.<result>__1);
this.$this.LoadData(this.<data>__2);
break;
default:
return;
}
}
catch (Exception exception) { ... }
this.$PC = -1;
this.$builder.SetResult();
}
ReadDataFromUrl_MoveNext
try {
catch (Exception exception) { . . . }

15. Quick Review

16. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/

17. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/

18. Let’s Fix Some
Code

19. Async/Await
Best Practices

20. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/

21. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/

22. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/

23. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/

24. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/

25. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/

26. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/

27. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/

28. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/
https://codetraveler.io/AsyncAwaitBestPractices/

29. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/
https://codetraveler.io/AsyncAwaitBestPractices/

30. @TheCodeTraveler https://codetraveler.io/AsyncAwaitBestPractices/