50 lines
2.0 KiB
C#
50 lines
2.0 KiB
C#
using System.ComponentModel.DataAnnotations.Resources;
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using System.Diagnostics.CodeAnalysis;
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namespace System.ComponentModel.DataAnnotations {
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/// <summary>
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/// Validation attribute to indicate that a property field or parameter is required.
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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 RequiredAttribute : ValidationAttribute {
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/// <summary>
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/// Default constructor.
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/// </summary>
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/// <remarks>This constructor selects a reasonable default error message for <see cref="ValidationAttribute.FormatErrorMessage"/></remarks>
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public RequiredAttribute()
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: base(() => DataAnnotationsResources.RequiredAttribute_ValidationError) {
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}
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/// <summary>
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/// Gets or sets a flag indicating whether the attribute should allow empty strings.
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/// </summary>
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public bool AllowEmptyStrings { get; set; }
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/// <summary>
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/// Override of <see cref="ValidationAttribute.IsValid(object)"/>
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/// </summary>
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/// <param name="value">The value to test</param>
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/// <returns><c>false</c> if the <paramref name="value"/> is null or an empty string. If <see cref="RequiredAttribute.AllowEmptyStrings"/>
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/// then <c>false</c> is returned only if <paramref name="vale"/> is null.</returns>
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#if !SILVERLIGHT
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public
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#else
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internal
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#endif
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override bool IsValid(object value) {
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if (value == null) {
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return false;
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}
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// only check string length if empty strings are not allowed
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var stringValue = value as string;
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if (stringValue != null && !AllowEmptyStrings) {
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return stringValue.Trim().Length != 0;
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}
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return true;
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}
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}
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}
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