Asp.Net MVC3模型验证字符串为null，如果不是，则最小长度为x [英] Asp.Net MVC3 Model Validation string is null or if not, has min length of x

问题描述

很好奇，是否可以让模型验证执行以下操作:

Just curious, is it possible to have Model Validation do the following:

NewPassword可以为null 或者 如果NewPassword不为null，则最小长度为7

NewPassword can be null OR If NewPassword is not null, then have a min length of 7

推荐答案

使用现成的功能，我认为这是不可能的.

Using the out of the box functionality, I don't believe this is possible.

但是，当然可以通过创建自己的自定义ValidationAttribute:

However, it is certainly possible by creating your own custom ValidationAttribute:

public class MinLengthOrNullAttribute : ValidationAttribute
{
    public int MinLength { get; set; }

    public MinLengthOrNullAttribute(int minLength)
    {
        MinLength = minLength;
    }

    public override Boolean IsValid(Object value)
    {
        return value == null || (value as string).Length > minLength;
    }
}

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