CreditCardAttribute.cs

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namespace System.ComponentModel.DataAnnotations;
 
[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, AllowMultiple = false)]
public sealed class CreditCardAttribute : DataTypeAttribute
{
    public CreditCardAttribute()
        : base(DataType.CreditCard)
    {
        base.DefaultErrorMessage = System.SR.CreditCardAttribute_Invalid;
    }
 
    public override bool IsValid(object? value)
    {
        if (value == null)
        {
            return true;
        }
        if (!(value is string text))
        {
            return false;
        }
        string text2 = text.Replace("-", string.Empty);
        text2 = text2.Replace(" ", string.Empty);
        int num = 0;
        bool flag = false;
        for (int num2 = text2.Length - 1; num2 >= 0; num2--)
        {
            char c = text2[num2];
            if (c < '0' || c > '9')
            {
                return false;
            }
            int num3 = (c - 48) * ((!flag) ? 1 : 2);
            flag = !flag;
            while (num3 > 0)
            {
                num += num3 % 10;
                num3 /= 10;
            }
        }
        return num % 10 == 0;
    }
}