RegularExpressionAttribute.cs

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using System.Globalization;
using System.Text.RegularExpressions;
 
namespace System.ComponentModel.DataAnnotations;
 
[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, AllowMultiple = false)]
public class RegularExpressionAttribute : ValidationAttribute
{
    public int MatchTimeoutInMilliseconds { get; set; }
 
    public string Pattern { get; }
 
    private Regex? Regex { get; set; }
 
    public RegularExpressionAttribute(string pattern)
        : base(() => System.SR.RegexAttribute_ValidationError)
    {
        Pattern = pattern;
        MatchTimeoutInMilliseconds = 2000;
    }
 
    public override bool IsValid(object? value)
    {
        SetupRegex();
        string text = Convert.ToString(value, CultureInfo.CurrentCulture);
        if (string.IsNullOrEmpty(text))
        {
            return true;
        }
        Match match = Regex.Match(text);
        if (match.Success && match.Index == 0)
        {
            return match.Length == text.Length;
        }
        return false;
    }
 
    public override string FormatErrorMessage(string name)
    {
        SetupRegex();
        return string.Format(CultureInfo.CurrentCulture, base.ErrorMessageString, name, Pattern);
    }
 
    private void SetupRegex()
    {
        if (Regex == null)
        {
            if (string.IsNullOrEmpty(Pattern))
            {
                throw new InvalidOperationException(System.SR.RegularExpressionAttribute_Empty_Pattern);
            }
            Regex = ((MatchTimeoutInMilliseconds == -1) ? new Regex(Pattern) : new Regex(Pattern, RegexOptions.None, TimeSpan.FromMilliseconds(MatchTimeoutInMilliseconds)));
        }
    }
}