ASP.NET MVC 模型的自定义验证

[TOC]

## CustomValidationAttribute

使用CustomValidationAttribute类实现模型的自定义验证，CustomValidationAttribute类继承了ValidationAttribute类

**命名空间：**System.ComponentModel.DataAnnotations

```csharp
public CustomValidationAttribute(Type validatorType, string method);
```

### 示例邮箱的验证

+ 邮箱字段
```csharp
/// <summary>
/// 邮箱验证
/// </summary>
public interface _IF_AddressList
{
   /// <summary>
   /// 邮箱
   /// </summary>
   [CustomValidation(typeof(EmailValidation), "Email")]
   [MaxLength(200, ErrorMessage = "邮箱字段的长度不能超过200个字符串")]
   string Email { get; set; }
}
```

+ 验证邮箱的方法
```csharp
/// <summary>
/// 邮箱验证
/// </summary>
public static class EmailValidation
{
    public static ValidationResult Email(string value)
    {
        var errors = new System.Text.StringBuilder();
        if (value != null)
        {
            string email = @"^([\w-.]+)@(([[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.)|(([\w-]+.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(]?)$";
            Regex Rg = new Regex(email);
            if (!Rg.IsMatch(value))
            {
                errors.AppendLine("邮箱地址输入有误！");
            }
        }
        if (errors.Length > 0)
            return new ValidationResult(errors.ToString());
        else
            return ValidationResult.Success;
    }
}
```

### 示例重写IsValid

+ 使用重写IsValid方法来实现自定义模型的验证
```csharp
// 验证下拉选择必选值（选择的值必须大于0）
public interface _IF_AddressList
{
   /// <summary>
   /// 运营商
   /// </summary>
   [RequiredSelect]
   [Display(Name = "运营商")]
   int Operators { get; set; }
}
```

+ 重写IsValid方法需要继承ValidationAttribute类
```csharp
/// <summary>
/// 必须填写大于0的数值
/// </summary>
[AttributeUsage(AttributeTargets.Property, AllowMultiple = true)]
public class RequiredSelect : ValidationAttribute
{
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        var errors = new System.Text.StringBuilder();
        if (value != null)
        {
            int val = int.Parse(value.ToString());
            if (val == 0)
            {
                errors.Append(validationContext.DisplayName + "必须选择！");
            }
        }
        else
        {
            errors.AppendLine(validationContext.DisplayName + "必须选择！");
        }
        if (errors.Length > 0)
            return new ValidationResult(errors.ToString());
        else
            return ValidationResult.Success;
    }
}
```