无法将新对象添加到列出过去的索引0

Question

我注意到我无法添加到索引0之后的对象列表。其他任何索引都返回空引用。

public class MultiValidation
{
    public List<SingleValidation> validations { get; set; }

    public MultiValidation(List<string> numArray)
    {

        for(int i = 0; i<numArray.Count; i++)
        {
            SingleValidation individual = new SingleValidation(Validate.idArray[i], Validate.actionArray[i], Validate.expiryArray[i]);
            validations = new List<SingleValidation>();
            validations.Add(individual);
            Console.WriteLine(validations[i].action);
        }
    }

这里是SingleValidation

使用的构造函数

public SingleValidation(string ide, string ac, string exDate)
{
    this.action = ac;
    this.expiry = exDate;
    this.id = ide;
}

我已经测试过idArray[i]，actionArray[i]，expiryArray[i]都是字符串。

Answer 1

validations = new List<SingleValidation>();

这应该在for循环之外。

{
validations = new List<SingleValidation>();
for(int i = 0; i<numArray.Count; i++)
    {
        SingleValidation individual = new SingleValidation(Validate.idArray[i], 
        Validate.actionArray[i], Validate.expiryArray[i]);
        validations.Add(individual);
        Console.WriteLine(validations[i].action);
    }
}