如何在自定义验证属性中访问视图模型的属性值以更改消息
本文关键字:属性 消息 模型 访问 自定义 验证 视图 | 更新日期: 2023-09-27 18:31:54
视图模型有许多字符串属性,如下所示Sample
。我的要求是根据视图模型中的布尔标志显示不同的验证消息。该标志是IsProposer
属性,如下所述:
[SampleAttribute(true, "bla prop", "foo add driver")]
public string Sample { get; set; }
public bool IsProposer { get; set; }
我想创建一个验证属性,以便我可以将其放置在我的所有字符串属性上(必需的验证)。然后根据该布尔标志的值,我将相应地传递 msg。我的自定义验证属性如下所示:
[AttributeUsage(AttributeTargets.Property, AllowMultiple = true, Inherited = false)]
public class SampleAttribute : RequiredAttribute
{
protected string ProposerErrorMessage { get; set; }
protected string AdditionalDriverErrorMessage { get; set; }
protected bool IsProposer { get; set; }
public SampleAttribute(bool isProposer, string propmsg, string adddrivermsg)
{
ProposerErrorMessage = propmsg;
IsProposer = isProposer;
AdditionalDriverErrorMessage = adddrivermsg;
}
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
if (IsValid(value))
{
return ValidationResult.Success;
}
else
{
return new ValidationResult(IsProposer ? ProposerErrorMessage : AdditionalDriverErrorMessage);
}
}
}
现在的问题是,如您所见,我只是将 true 作为属性的第一个参数传递。在这里,我需要从视图模型实例传递 Isproposer
属性的值,以便我可以相应地采取行动。如何访问它?
我通过创建这样的属性解决了我的问题:
/// <summary>
/// This validation attribute is an extension to RequiredAttribute that can be used to choose either of the two
/// validation messages depending on a property in the context of same model.
/// </summary>
[AttributeUsage(AttributeTargets.Property, AllowMultiple = true, Inherited = false)]
public class RequiredExtensionAttribute : RequiredAttribute
{
private string _errorMessageIfTruthy;
private string _errorMessageIfFalsy;
private string _dependentProperty;
public RequiredExtensionAttribute(string dependentproperty, string errorMessageIfTruthy, string errorMessageIfFalsy)
{
_errorMessageIfTruthy = errorMessageIfTruthy;
_dependentProperty = dependentproperty;
_errorMessageIfFalsy = errorMessageIfFalsy;
}
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
var propertyTestedInfo = validationContext.ObjectType.GetProperty(this._dependentProperty);
if (propertyTestedInfo == null)
{
return new ValidationResult(string.Format("unknown property {0}", this._dependentProperty));
}
var propertyTestedValue = propertyTestedInfo.GetValue(validationContext.ObjectInstance, null);
if (IsValid(value))
{
return ValidationResult.Success;
}
else
{
return new ValidationResult((bool)propertyTestedValue ? _errorMessageIfTruthy : _errorMessageIfFalsy);
}
}
}
现在可以在以下模型中使用:
[RequiredExtensionAttribute("IsProposerViewModel", "Please select your employment status.", "Please select this driver's employment status")]
public string EmploymentStatus { get; set; }
public bool IsProposerViewModel { get; set; }
-其中属性的第一个参数是IsProposerViewModel
,依赖值。