[API Proposal]: ArgumentException.ThrowIfNullOrWhitespace

[linkdotnet]

Background and motivation

.NET 7 introduced a new helper method: ArgumentException.ThrowIfNullOrEmpty(), which throws an ArgumentNullException when the string is null and ArgumentException when the string is empty.

In lots of use-case scenarios an empty strings is equal to a string which purely consist out of whitespaces. Let's say a GitHub username is invalid either way: Null, empty or full of blanks or tabs. There are lots of scenarios where user input is only valid if there are printable characters.

To remove the boiler plate code and align how user would write code a new ThrowIfNullOrWhitespace could be introduced.

API Proposal

public class ArgumentException
{
    public static void ThrowIfNullOrWhitespace(string argument, [CallerArgumentExpression("argument")] string? paramName = null)
    {
        if (string.IsNullOrWhitespace(argument))
        {
            ArgumentNullException.ThrowIfNull(argument, paramName);
            throw new ArgumentException("String should not be empty or have only whitespaces", paramName);
        }
    }
}

API Usage

public void AddUser(string? username)
{
    ArgumentException.ThrowIfNullOrWhitespace(username);
}

Alternative Designs

No response

Risks

No response

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Issue Details

---

Background and motivation

.NET 7 introduced a new helper method: ArgumentException.ThrowIfNullOrEmpty(), which throws an ArgumentNullException when the string is null and ArgumentException when the string is empty.

In lots of use-case scenarios an empty strings is equal to a string which purely consist out of whitespaces. Let's say a GitHub username is invalid either way: Null, empty or full of blanks or tabs. There are lots of scenarios where user input is only valid if there are printable characters.

To remove the boiler plate code and align how user would write code a new ThrowIfNullOrWhitespace could be introduced.

API Proposal

public class ArgumentException
{
    public static void ThrowIfNullOrWhitespace(string argument, [CallerArgumentExpression("argument")] string? paramName = null)
    {
        if (string.IsNullOrWhitespace(argument))
        {
            ArgumentNullException.ThrowIfNull(argument, paramName);
            throw new ArgumentException("String should not be empty or have only whitespaces", paramName);
        }
    }
}

API Usage

public void AddUser(string? username)
{
    ArgumentException.ThrowIfNullOrWhitespace(username);
}

Alternative Designs

No response

Risks

No response

Author:	linkdotnet
Assignees:	-
Labels:	api-suggestion, area-System.Runtime, untriaged
Milestone:	-

[GSPP]

This is certainly a reasonable piece of logic to have and I understand the desire to have a helper method for this. That being said, this is a very specific use case that isn't common enough across the .NET ecosystem to warrant a built-in helper. All kinds of variations of this kind of logic come to mind.

I solve the "whitespace problem" in user input like this:

var input = ...;

var trimmed = input.Trim();
if (trimmed.Length == 0) ... //Error case

UseUserInput(trimmed); //Reuse the trimmed string for further processing

This is the form of logic that my projects have needed many times. My logic is slightly different from yours, making my point.

I have a helper method just for this, and it would not have any business being in the BCL because it is overly specific.

[linkdotnet]

Fair point and I do understand your reasoning. That said, we can close the proposal.