MaxLengthAttribute.cs

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using System.Diagnostics.CodeAnalysis;
using System.Globalization;
 
namespace System.ComponentModel.DataAnnotations;
 
[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, AllowMultiple = false)]
public class MaxLengthAttribute : ValidationAttribute
{
    public int Length { get; }
 
    private static string DefaultErrorMessageString => System.SR.MaxLengthAttribute_ValidationError;
 
    [RequiresUnreferencedCode("Uses reflection to get the 'Count' property on types that don't implement ICollection. This 'Count' property may be trimmed. Ensure it is preserved.")]
    public MaxLengthAttribute(int length)
        : base(() => DefaultErrorMessageString)
    {
        Length = length;
    }
 
    [RequiresUnreferencedCode("Uses reflection to get the 'Count' property on types that don't implement ICollection. This 'Count' property may be trimmed. Ensure it is preserved.")]
    public MaxLengthAttribute()
        : base(() => DefaultErrorMessageString)
    {
        Length = -1;
    }
 
    [UnconditionalSuppressMessage("ReflectionAnalysis", "IL2026:RequiresUnreferencedCode", Justification = "The ctors are marked with RequiresUnreferencedCode.")]
    public override bool IsValid(object? value)
    {
        EnsureLegalLengths();
        if (value == null)
        {
            return true;
        }
        int num;
        if (value is string text)
        {
            num = text.Length;
        }
        else
        {
            if (!CountPropertyHelper.TryGetCount(value, out var count))
            {
                throw new InvalidCastException(System.SR.Format(System.SR.LengthAttribute_InvalidValueType, value.GetType()));
            }
            num = count;
        }
        if (-1 != Length)
        {
            return num <= Length;
        }
        return true;
    }
 
    public override string FormatErrorMessage(string name)
    {
        return string.Format(CultureInfo.CurrentCulture, base.ErrorMessageString, name, Length);
    }
 
    private void EnsureLegalLengths()
    {
        if (Length == 0 || Length < -1)
        {
            throw new InvalidOperationException(System.SR.MaxLengthAttribute_InvalidMaxLength);
        }
    }
}