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using System.ComponentModel.DataAnnotations.Resources;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
namespace System.ComponentModel.DataAnnotations {
/// <summary>
/// Specifies the maximum length of array/string data allowed in a property.
/// </summary>
[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, AllowMultiple = false)]
[SuppressMessage("Microsoft.Performance", "CA1813:AvoidUnsealedAttributes", Justification = "We want users to be able to extend this class")]
public class MaxLengthAttribute : ValidationAttribute {
private const int MaxAllowableLength = -1;
/// <summary>
/// Gets the maximum allowable length of the array/string data.
/// </summary>
public int Length { get; private set; }
/// <summary>
/// Initializes a new instance of the <see cref="MaxLengthAttribute"/> class.
/// </summary>
/// <param name="length">
/// The maximum allowable length of array/string data.
/// Value must be greater than zero.
/// </param>
public MaxLengthAttribute(int length)
: base(() => DefaultErrorMessageString) {
Length = length;
}
/// <summary>
/// Initializes a new instance of the <see cref="MaxLengthAttribute"/> class.
/// The maximum allowable length supported by the database will be used.
/// </summary>
public MaxLengthAttribute()
: base(() => DefaultErrorMessageString) {
Length = MaxAllowableLength;
}
private static string DefaultErrorMessageString {
get { return DataAnnotationsResources.MaxLengthAttribute_ValidationError; }
}
/// <summary>
/// Determines whether a specified object is valid. (Overrides <see cref = "ValidationAttribute.IsValid(object)" />)
/// </summary>
/// <remarks>
/// This method returns <c>true</c> if the <paramref name = "value" /> is null.
/// It is assumed the <see cref = "RequiredAttribute" /> is used if the value may not be null.
/// </remarks>
/// <param name = "value">The object to validate.</param>
/// <returns><c>true</c> if the value is null or less than or equal to the specified maximum length, otherwise <c>false</c></returns>
/// <exception cref = "InvalidOperationException">Length is zero or less than negative one.</exception>
public override bool IsValid(object value) {
// Check the lengths for legality
EnsureLegalLengths();
var length = 0;
// Automatically pass if value is null. RequiredAttribute should be used to assert a value is not null.
if (value == null) {
return true;
}
else {
var str = value as string;
if (str != null) {
length = str.Length;
}
else {
// We expect a cast exception if a non-{string|array} property was passed in.
length = ((Array)value).Length;
}
}
return MaxAllowableLength == Length || length <= Length;
}
/// <summary>
/// Applies formatting to a specified error message. (Overrides <see cref = "ValidationAttribute.FormatErrorMessage" />)
/// </summary>
/// <param name = "name">The name to include in the formatted string.</param>
/// <returns>A localized string to describe the maximum acceptable length.</returns>
public override string FormatErrorMessage(string name) {
// An error occurred, so we know the value is greater than the maximum if it was specified
return string.Format(CultureInfo.CurrentCulture, ErrorMessageString, name, Length);
}
/// <summary>
/// Checks that Length has a legal value.
/// </summary>
/// <exception cref="InvalidOperationException">Length is zero or less than negative one.</exception>
private void EnsureLegalLengths() {
if (Length == 0 || Length < -1) {
throw new InvalidOperationException(String.Format(CultureInfo.CurrentCulture, DataAnnotationsResources.MaxLengthAttribute_InvalidMaxLength));
}
}
}
}
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