Ellersoft.Strings

A type-safe string validation framework.

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Purpose

One of the biggest .NET shortcomings, in my opinion, is there's no way to guarantee the type-safety of strings to certain contracts. That is: how can we guarantee a string is an Email, for example?

This project seeks to provide a base for a solution to that problem. By utilizing this structure, it is trivial to create type-safe (runtime-verified, for now) string references. This can be used to guarantee that a string meets a certain contract.

Examples

One can implement the ValidatedString abstract class to create new validations, for example, the aforementioned Email string validation can be created with the following class which will inherit from RegexString:

public class StringEmail : RegexString
{
    protected override string ErrorRequirement => "be a valid email of the format <example>@<example>.<com>";
    protected override string RegexValidation => @"^.+@.+\..+$";
    protected override bool AllowNull => false;

    protected StringEmail() { }
    public StringEmail(string str) : base(str) { }
}

This allows one to create a contract for said string, such that they may use StringEmail as the type for an object, such as the following:

public class Test
{
    public StringEmail Email { get; set; }
}

Now, it requires one to always ensure that the string is safe.

Conversion from string

Additionally, if you don't want to have to manually call the String<X>(string) constructor, you can specify an implicit or explicit conversion operator on the String<X> type:

public static explicit operator StringEmail(string str) => new StringEmail(str);

A basic template for it is:

public static explicit operator String<...>(string str) => new String<...>(str);

Additional Notes

The following built-in string components are defined (also with the explicit operator):

• NonEmptyString: verifies that a string does not pass System.String.IsNullOrWhitespace;
• StringAlpha: verifies that a string is alpha-only (a-z in either case);
• StringAlphaNum: verifies that a string is alpha-numeric-only (0-9, a-z in either case);
• StringHex: verifies that a string is hexadecimal-only (0-9, a-f in either case);
• StringHexPrefix: verifies that a string is hexadecimal-only (0-9, a-f in either case) with an optional prefix (0x or &H);
• StringNum: verifies that a string is numeric-only (0-9);