Question

I’m trying to figure out if there is an easy way implementing a retry to the service when it sends a fault. lets say for eg:

Private Function SaveEmployee(emp as Empoyee)
Try
...
returnval = service.SaveEmployee(emp)
Catch ex as exception
'if exception requires retry eg:end point not found or database is not responding then
'call retry  func/class

RetryOperation(...) 

End Try

End Function

in the above sample how can I make a generic RetryOperation class which can take any function and call it 3 or 4 times with an interval before informing the user that the operation cannot be completed.

I’m hoping it’s possible to make a generic method rather than have duplicate code in all the service call functions

any samples in C# or vb.net will be really appreciated.

Thanks

Answer 1

If it is a call that you might want repeated if it fails why not use the Repeat functionality at once, if the service call is successful it will just be called once, if the service call fails it will retry x number of times, if it fails on the x:th time it will throw an exception

How about something like this, please note this is greatly simplified, you will need to add error handling and such:

Create your repeat method like this:

private void RepeatCall(int numberOfCalls, Action unitOfWork)
{
    for (int i = 1; i <= numberOfCalls; i++)
        {
        try
        {
            unitOfWork();
        }
        catch (...)
        {
            // decide which exceptions/faults should be retried and 
            // which should be thrown
            // and always throw when i == numberOfCalls
        }
     }
 }

Use it like this

try
{
    RepeatCall(3, () => 
                    {
                         MyServiceCall();
                    });

}
catch(....)
{
   // You'll catch here same as before since on the last try if the call
   // still fails you'll get the exception
}

Same thing in VB.NET

Private Sub RepeatCall(ByVal numberOfCalls As Integer, ByVal unitOfWork As Action)

    For i = 1 To numberOfCalls
        Try
            unitOfWork()
        Catch ex As Exception

        End Try
    Next

End Sub

Use it:

  Try
      RepeatCall(3, Sub()
                       MyServiceCall()
                    End Sub)

  Catch ex As Exception

  End Try