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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Collections.Generic;
namespace System.ComponentModel.DataAnnotations
{
/// <summary>
/// Container class for the results of a validation request.
/// <para>
/// Use the static <see cref="ValidationResult.Success" /> to represent successful validation.
/// </para>
/// </summary>
/// <seealso cref="ValidationAttribute.GetValidationResult" />
public class ValidationResult
{
#region Member Fields
/// <summary>
/// Gets a <see cref="ValidationResult" /> that indicates Success.
/// </summary>
/// <remarks>
/// The <c>null</c> value is used to indicate success. Consumers of <see cref="ValidationResult" />s
/// should compare the values to <see cref="ValidationResult.Success" /> rather than checking for null.
/// </remarks>
public static readonly ValidationResult? Success;
#endregion
#region All Constructors
/// <summary>
/// Constructor that accepts an error message. This error message would override any error message
/// provided on the <see cref="ValidationAttribute" />.
/// </summary>
/// <param name="errorMessage">
/// The user-visible error message. If null, <see cref="ValidationAttribute.GetValidationResult" />
/// will use <see cref="ValidationAttribute.FormatErrorMessage" /> for its error message.
/// </param>
public ValidationResult(string? errorMessage)
: this(errorMessage, null)
{
}
/// <summary>
/// Constructor that accepts an error message as well as a list of member names involved in the validation.
/// This error message would override any error message provided on the <see cref="ValidationAttribute" />.
/// </summary>
/// <param name="errorMessage">
/// The user-visible error message. If null, <see cref="ValidationAttribute.GetValidationResult" />
/// will use <see cref="ValidationAttribute.FormatErrorMessage" /> for its error message.
/// </param>
/// <param name="memberNames">
/// The list of member names affected by this result.
/// This list of member names is meant to be used by presentation layers to indicate which fields are in error.
/// </param>
public ValidationResult(string? errorMessage, IEnumerable<string>? memberNames)
{
ErrorMessage = errorMessage;
MemberNames = memberNames ?? Array.Empty<string>();
}
/// <summary>
/// Constructor that creates a copy of an existing ValidationResult.
/// </summary>
/// <param name="validationResult">The validation result.</param>
/// <exception cref="System.ArgumentNullException">The <paramref name="validationResult" /> is null.</exception>
protected ValidationResult(ValidationResult validationResult)
{
ArgumentNullException.ThrowIfNull(validationResult);
ErrorMessage = validationResult.ErrorMessage;
MemberNames = validationResult.MemberNames;
}
#endregion
#region Properties
/// <summary>
/// Gets the collection of member names affected by this result. The collection may be empty but will never be null.
/// </summary>
public IEnumerable<string> MemberNames { get; }
/// <summary>
/// Gets the error message for this result. It may be null.
/// </summary>
public string? ErrorMessage { get; set; }
#endregion
#region Methods
/// <summary>
/// Override the string representation of this instance, returning
/// the <see cref="ErrorMessage" /> if not <c>null</c>, otherwise
/// the base <see cref="object.ToString" /> result.
/// </summary>
/// <remarks>
/// If the <see cref="ErrorMessage" /> is empty, it will still qualify
/// as being specified, and therefore returned from <see cref="ToString" />.
/// </remarks>
/// <returns>
/// The <see cref="ErrorMessage" /> property value if specified,
/// otherwise, the base <see cref="object.ToString" /> result.
/// </returns>
public override string ToString() => ErrorMessage ?? base.ToString()!;
#endregion Methods
}
}
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