string-id.md

String IDs

Use [StringId] to generate a strongly typed identifier backed by string.

Basic example

using StrongTypeIdGenerator;

[StringId]
public sealed partial class OrderId
{
}

Generated behavior

A generated OrderId includes:

• Constructor that accepts string
• Value property (or custom name)
• Unspecified initialized with string.Empty
• Equality/comparison members and operators
• ToString() and ToString(string?, IFormatProvider?)
• Implicit conversions to and from string
• Nested TypeConverter

Custom validation

[StringId]
public sealed partial class OrderId
{
    private static string CheckValue(string value)
    {
        if (string.IsNullOrWhiteSpace(value))
            throw new ArgumentException("Order ID cannot be empty", nameof(value));

        return value.Trim().ToUpperInvariant();
    }
}

CheckValue is called from the generated constructor.

Custom value property name

[StringId(ValuePropertyName = "Code")]
public sealed partial class ProductCode
{
}

The generated property name becomes Code instead of Value.

Private constructor mode

[StringId(GenerateConstructorPrivate = true)]
public sealed partial class SessionToken
{
    public static SessionToken Create(string raw) => new SessionToken(raw);
}

Continue with custom validation and private constructors.