如何使用新的错误消息创建自定义MaxLength和Required验证，逻辑保持不变

本文关键字：验证 Required 何使用 错误 消息 MaxLength 自定义 创建 | 更新日期: 2023-09-27 18:17:30

[MaxLength(45, ErrorMessage = Translations.Attribute.MAX_LENGTH)]
[Required(ErrorMessage = Translations.Attribute.REQUIRED)]

如何使用默认翻译消息创建自定义Required和MaxLength验证。我可以简单地重写它并只更改errorMessage吗?

我只想写

[MyMaxLength(45)]
[MyRequired]

所需创建的解决方案:

public class MyRequiredAttribute : RequiredAttribute
    {
        public override string FormatErrorMessage(string name)
        {
            return string.Format("Polje {0} je obvezno", name);
        }
    }

如何使用新的错误消息创建自定义MaxLength和Required验证，逻辑保持不变

你应该能够从MaxLengthAttribute，或任何其他属性你正在使用…

public class MyMaxLengthAttribute : MaxLengthAttribute
{
    public MyMaxLengthAttribute(int length) : base(length)
    {
        ErrorMessage = Translations.Attribute.MAX_LENGTH;
    }
    // other ctors/members as needed
}

对于任何正在使用MVC并想要自定义或本地化MaxLength错误消息的人。

1)创建自己的MaximumLengthAttribute，从MaxLength派生，使用一个资源文件。

2)创建一个MaximumLengthValidator，利用MaxLength规则。

3)在Application_Start

中注册MaximumLenghtAttribute和Validator

4)用MaximumLength(45)属性装饰你的属性。

using System;
using System.ComponentModel.DataAnnotations;
public class MaximumLengthAttribute : MaxLengthAttribute
{
    /// <summary>
    /// MaxLength with a custom and localized error message
    /// </summary>
    public MaximumLengthAttribute(int maximumLength) : base(maximumLength)
    {
        base.ErrorMessageResourceName = "MaximumLength";
        base.ErrorMessageResourceType = typeof(Resources);
    }
}

和

using System.Collections.Generic;
using System.Web.Mvc;
public class MaximumLengthValidator : DataAnnotationsModelValidator
{
    private string _errorMessage;
    private MaximumLengthAttribute _attribute;
    public MaximumLengthValidator(ModelMetadata metadata, ControllerContext context, MaximumLengthAttribute attribute)
    : base(metadata, context, attribute)
    {
        _errorMessage = attribute.FormatErrorMessage(metadata.GetDisplayName());
        _attribute = attribute;
    }
    public override IEnumerable<ModelClientValidationRule> GetClientValidationRules()
    {
        var rule = new ModelClientValidationRule
        {
            // Uses MVC maxlength validator (but with a custom message from MaximumLength)
            ErrorMessage = this._errorMessage,
            ValidationType = "maxlength"
        };
        rule.ValidationParameters.Add("max", _attribute.Length);
        yield return rule;
    }
}

和Application_Start…

DataAnnotationsModelValidatorProvider.RegisterAdapter(typeof(MaximumLengthAttribute), typeof(MaximumLengthValidator));

在这种情况下，我创建的AppMaxLength属性是从MaxLengthAttribute继承的，MaxLength不固定，它可以在webconfig或DBConfig上更改，如果你想。

public class AppMaxLengthAttribute : MaxLengthAttribute, IClientValidatable
{
    public AppMaxLengthAttribute(string configName)
    : base(int.Parse(WebConfigurationManager.AppSettings[configName]))
    {
    }
    public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
    {
        var rule = new ModelClientValidationRule
        {
            ErrorMessage = FormatErrorMessage(metadata.GetDisplayName()),
            ValidationType = "maxlength"
        };
        rule.ValidationParameters.Add("max", this.Length);
        yield return rule;
    }
}

和应用:

    [AppMaxLength("NotFixedCodeLength", ErrorMessageResourceType = typeof(Resources), ErrorMessageResourceName = "MsgMaxLength")]       
    public string Code { get; set; }

webconfig的配置信息:

appSettings标签插入键

<add key="NotFixedCodeLength" value="10" />
对不起，我的英文不好。=)) 
using System.ComponentModel.DataAnnotations;        
[Required(ErrorMessage = "This field is required!!!")]
[MaxLength(30, ErrorMessage = "Max number of characters is 30 duh!")]
public string FirstName { get; set; }
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