Code comparation

Question 1:

Task pdfFile = CreatePdf(invoice, customer, invoiceInformationChanged, parameters); 
Task pdfChangedFile = CreatePdfChanged(invoice, customer, invoiceInformationChanged, parameters); 
Task xmlile = CreateXml(invoice, customer, invoiceInformationChanged, parameters); 
MemoryStream[] results = await Task.WhenAll(pdfFile, pdfChangedFile, xmlile);

is equivalent with these code??

 await CreatePdf(invoice, customer, invoiceInformationChanged, parameters); 
 await CreatePdfChanged(invoice, customer, invoiceInformationChanged, parameters); 
 await CreateXml(invoice, customer, invoiceInformationChanged, parameters);

Answer: No, the two approaches you've provided are not equivalent in terms of how the tasks are executed and performance.

Explanation of Both Approaches:

1. First Approach: Using Task.WhenAll:

   Task<MemoryStream> pdfFile = CreatePdf(invoice, customer, invoiceInformationChanged, parameters);
   Task<MemoryStream> pdfChangedFile = CreatePdfChanged(invoice, customer, invoiceInformationChanged, parameters);
   Task<MemoryStream> xmlile = CreateXml(invoice, customer, invoiceInformationChanged, parameters);
   MemoryStream[] results = await Task.WhenAll(pdfFile, pdfChangedFile, xmlile);

   • Parallel execution: All three tasks (CreatePdf, CreatePdfChanged, and CreateXml) are started and executed in parallel.

   • Faster completion: Since the tasks run concurrently, the total execution time will be roughly the time of the slowest task (assuming no dependencies between them).

   • Waiting: The await Task.WhenAll() waits for all tasks to complete before moving to the next line of code.

   This approach is faster because all tasks execute at the same time.

2. Second Approach: Sequential await:

   await CreatePdf(invoice, customer, invoiceInformationChanged, parameters); 
   await CreatePdfChanged(invoice, customer, invoiceInformationChanged, parameters); 
   await CreateXml(invoice, customer, invoiceInformationChanged, parameters);

   • Sequential execution: Each task is awaited in order. The first task (CreatePdf) must complete before the second task (CreatePdfChanged) starts, and the third task (CreateXml) starts only after the second finishes.

   • Slower completion: The total execution time will be the sum of the individual task durations, which is typically slower than parallel execution.

Conclusion:

• Task.WhenAll is faster because it runs the tasks in parallel and waits for all of them to complete.

• The sequential await approach is slower because it executes the tasks one by one.

Use Task.WhenAll if the tasks are independent and don't need to be executed in a specific order.