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