c# - 将值附加到现有 IEnumerable 的末尾时产生返回

Question

我刚知道yield return，我看起来很不错。我用这样的方法使用它:

public IEnumerable<ValidationResult> Validate(ValidationContext vc)
{
    if (Name == "Arbitary")
        yield return new ValidationResult("Bad Name.", new[] { "Name" });
    else if (Email == "BadEmail")
        yield return new ValidationResult("Bad Email.", new [] {"Email" });
    // further rules follow.
}

但是，我需要更改此方法以从子方法返回一些 ValidationResults。如果不使用 yield，代码将如下所示:

public override IEnumerable<ValidationResult> Validate(ValidationContext vc)
{
    // TryValidateObject fills the ICollection you pass it.
    List<ValidationResult> retVal = new List<ValidationResult>();
    Validator.TryValidateObject(this, vc, retVal, true);

    if (Name == "Arbitary")
        retVal.Add(new ValidationResult("Bad Name.", new[] { "Name" }));
    else if (Email == "BadEmail")
        retVal.Add(new ValidationResult("Bad Email.", new[] { "Email" }));

    return retVal;
}

是否可以使用 yield 重写它？

Answer 1

你在找这个吗？

public override IEnumerable<ValidationResult> Validate(ValidationContext vc)
{
    // TryValidateObject fills the ICollection you pass it.
    List<ValidationResult> retVal = new List<ValidationResult>();
    Validator.TryValidateObject(this, vc, retVal, true);
    foreach (var item in retVal)
        yield return item;
    if (Name == "Arbitary")
        yield return new ValidationResult("Bad Name.", new[] { "Name" });
    else if (Email == "BadEmail")
        yield return new ValidationResult("Bad Email.", new[] { "Email" });       
}

如果是这样，我相信第一个版本看起来更好。