System.ArgumentNullException: 'String reference not set to an instance of a String. Parameter name: s'

Question

When i submit the registration form i get this error:

System.ArgumentNullException: 'String reference not set to an instance of a String. Parameter name: s'

it's coming form the hashing password class

public static class Crypto
{
    public static string Hash(string value)
    {
        return Convert.ToBase64String(
            SHA256.Create()
                .ComputeHash(Encoding.UTF8.GetBytes(value)));
    }
}

Answer 1

Check value for null (or empty) before calling the rest of the methods:

public static string Hash(string value)
{
    if (String.IsNullOrEmpty(value))
        throw new ArgumentNullException(nameof(value));

    var bytes = Encoding.UTF8.GetBytes(value);
    var hash = SHA256.Create().ComputeHash(bytes)
    return Convert.ToBase64String(hash);
}

Having each method's result in its own variable will also help you to debug and better understand the flow.