C# – ApplicationException or create custom exceptions


In my file repository, I will throw the following exceptions when the InsertFile() method is called:

  • When the upload file size limit is exceeded
  • When the storage capacity is exceeded

At the moment I am just throwing an ApplicationException with the relevant message:

public void InsertFile(HttpPostedFile uploadedFile)
    if (uploadedFile.ContentLength > FileSizeLimit)
        throw new ApplicationException("File size limit exceeded.");

    if (uploadedFile.ContentLength + FileStorageUsage > FileStorageCapacity)
        throw new ApplicationException("File storage capacity exceeded.");

    // ...


Are there better exception classes that I should be using here?

Or should I be creating my own custom exceptions by deriving from ApplicationException?

Best Solution

Maybe read the documentation:

If you are designing an application that needs to create its own exceptions, you are advised to derive custom exceptions from the Exception class. It was originally thought that custom exceptions should derive from the ApplicationException class; however in practice this has not been found to add significant value.

As to whether there are better exceptions to throw - some might consider throwing an ArgumentOutOfRangeException if you don't want to define your own exception.