Question 85738 in ASP.NET Question posted in
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How to write a try catch statement where I need to check two things – Asp.net

I have a method which have a try catch clause where I parse a mobile phone number.
If parsing goes OK, the code outside the try continues to execute.
If parsing encounters an error, I enter the catch and raise the error.

All this was OK until I got a request to check for another phone number.

I am not sure how to do it because later in the code I need at least one correct phone number (its not important which one).

If I put both parsing inside one try, I have a problem if first one is wrong and second is good because exception will be raised anyway.

try {
    model.mobilePhone = PhoneParser.Parse(m.mobile);
    model.alternativePhoneNumber = PhoneParser.Parse(m.alternativePhoneNumber);
}

catch (Exception) {
    _log.LogWarning("Error while parsing the phone number")
}

return model;

Maybe something like this? Try inside a catch?

try {
    model.mobilePhone = PhoneParser.Parse(m.mobile);
}

catch (Exception) {
    try {
         model.alternativePhoneNumber = PhoneParser.Parse(m.alternativePhoneNumber);
  }
     catch (Exception) {
         _log.LogWarning("Error while parsing the alternative phone number")
  }
    _log.LogWarning("Error while parsing the mobile phone number")
}

return model;
Tags:

3

Answers


  1. 0

    I advise against nesting try-catches.

    Use two separate try-catches for each field (model.PhoneNumber and model.AlternativePhoneNumber).

    Although the best way of solving your issue would be creating a separate .TryParse() extension method for phone number and using that. This would also conform your code to DRY (do not repeat yourself) principle.

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  2. 0

    If all you need is one valid phone number, create a little helper method in your model called EnsureValidState

    public void EnsureValidState()
{
   if(this.mobilePhone == null && this.alternativePhoneNumber ==null) 
   {
     //no valid state, raise exception
   }
    
    //other validation for different rules.
}

    Call this method, after all your properties are set and validate accordingly.
    You could even abstract this away into an abstract base class for your entities:

    public abstract class BaseEntity
{
   private abstract void EnsureValidState();
}

    If you want to go a step further have a look at the Hands on DDD example code over at https://github.com/PacktPublishing/Hands-On-Domain-Driven-Design-with-.NET-Core/blob/086cabf75211daa8df9d2117dec0181a0339749d/Marketplace.Framework/Entity.cs, that will give you an idea on how to implement a more generic way to ensure consistent updates on your entites and models.

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  3. 0

    The simplest answer is to have two separate try/catch blocks. Otherwise, the alternate phone number will only ever get added if the primary phone number fails (but it’s likely that if they supplied both, both are valid).

    try 
{
    model.mobilePhone = PhoneParser.Parse(m.mobile);
}
catch (Exception e)
{
    _log.LogWarning($"Error while parsing the mobile phone number:rn{e}")
}

try 
{
    model.alternativePhoneNumber = PhoneParser.Parse(m.alternativePhoneNumber);
}
catch (Exception e) 
{
    _log.LogWarning($"Error while parsing the alternative phone number:rn{e}")
}

return model;

    As others have suggested, implementing a TryParse might be helpful, but then you’ll lose the exception information that you’re currently logging now. Also, the TryParse should not wrap calls to Parse in try/catch blocks, because exception handling is expensive. Instead it should use the same logic as the Parse method, but return false instead of throwing an exception.

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