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Asked: 2026-05-10T18:52:08+00:00

The title may not really explain what I’m really trying to get at, couldn’t

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The title may not really explain what I’m really trying to get at, couldn’t really think of a way to describe what I mean.

I was wondering if it is good practice to check the arguments that a function accepts for nulls or empty before using them. I have this function which just wraps some hash creation like so.

Public Shared Function GenerateHash(ByVal FilePath As IO.FileInfo) As String         If (FilePath Is Nothing) Then             Throw New ArgumentNullException('FilePath')         End If          Dim _sha As New Security.Cryptography.MD5CryptoServiceProvider         Dim _Hash = Convert.ToBase64String(_sha.ComputeHash(New IO.FileStream(FilePath.FullName, IO.FileMode.Open, IO.FileAccess.Read)))         Return _Hash     End Function

As you can see I just takes a IO.Fileinfo as an argument, at the start of the function I am checking to make sure that it is not nothing.

I’m wondering is this good practice or should I just let it get to the actual hasher and then throw the exception because it is null.?

Thanks.

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1 Answer

  1. In general, I’d suggest it’s good practice to validate all of the arguments to public functions/methods before using them, and fail early rather than after executing half of the function. In this case, you’re right to throw the exception.

    Depending on what your method is doing, failing early could be important. If your method was altering instance data on your class, you don’t want it to alter half of the data, then encounter the null and throw an exception, as your object’s data might them be in an intermediate and possibly invalid state.

    If you’re using an OO language then I’d suggest it’s essential to validate the arguments to public methods, but less important with private and protected methods. My rationale here is that you don’t know what the inputs to a public method will be – any other code could create an instance of your class and call it’s public methods, and pass in unexpected/invalid data. Private methods, however, are called from inside the class, and the class should already have validated any data passing around internally.

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