MaxLength 属性取决于消耗 class

Question

如何在多个 class 消耗的 class 上设置不同的 MaxLength 属性，其中每个消耗 class.

的 MaxLength 可以不同

就我而言，我使用的是 Entity Framework 和 MVC。我的 BilingualStrings 实体数据模型中有一个复杂类型，它由英语和法语字符串组成。我有许多具有双语字符串的实体，该字符串使用复杂类型将英语和法语映射到正确的数据库 table/column。所以每个 table 有两列，但实体有一个属性类型的 BilingualString。单个 table 中每个英语或法语的字段长度始终相同，但每个 table.

的字段长度可能不同

这是我要实现的目标的简化示例：

public partial class BilingualString
{
    //[MaxLength(40)]  Cannot put MaxLength here because it would apply to all instances of BilingualString
    public string English { get; set; }
    public string French { get; set; }
}

public class ClassWithShortDescription
{
    //[MaxLength(20)] Cannot put MaxLength here because it does not makes sense.  It needs to be on each English and French properties.
    public BilingualString Description { get; set; }
}

public class ClassWithLongDescription
{
    //[MaxLength(200)] Cannot put MaxLength here because it does not makes sense.  It needs to be on each English and French properties.
    public BilingualString Description { get; set; }
}

Answer 1

由于英语和法语在 BilingualString 中是硬编码的，您还可以硬编码两个属性而不是一个：

public class ClassWithShortDescription
{
    [MaxLengthForEnglish(20)]
    [MaxLengthForFrench(25)]
    public BilingualString Description { get; set; }
}

public class ClassWithLongDescription
{
    [MaxLengthForEnglish(200)]
    [MaxLengthForFrench(250)]
    public BilingualString Description { get; set; }
}

Answer 2

经过一些阅读和大量谷歌搜索后，我得出结论，潜在的问题是由数据属性设置的元数据是静态的。因此，嵌套的 class 属性不能有不同的元数据，即使被不同的 classes 使用也是如此。解决方案是将元数据放在消费 class 的属性上。创建应用于 BilingualString 类型的属性的自定义 maxlength 属性。

双语字符串的自定义 MaxLength 属性 public class 最大长度双语字符串属性：最大长度属性 { public MaxLengthBilingualStringAttribute(int length) : base(length) { }

    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        BilingualString bilingualString = new BilingualString();
        if (value.GetType() == typeof(EdmBilingualStringVarCharSingleLine))
        {
            var bs = value as EdmBilingualStringVarCharSingleLine;
            bilingualString.English = bs.English;
            bilingualString.French = bs.French;
        }
        else
            return new ValidationResult("MaxLengthBilingualString Attribute does cannot be used with this type.");
        if (bilingualString.English != null && bilingualString.English.Length > this.Length )
            return new ValidationResult(string.Format("The maximum field length of {0} has been exceed for {1} English.", this.Length, validationContext.DisplayName));
        if (bilingualString.French != null && bilingualString.French.Length > this.Length)
            return new ValidationResult(string.Format("The maximum field length of {0} has been exceed for {1} French.", this.Length, validationContext.DisplayName));
        return ValidationResult.Success;
    }
}

示例实现：

public partial class BilingualString
{
    public string English { get; set; }
    public string French { get; set; }
}

public class ClassWithShortDescription
{
    [MaxLengthBilingualString(20)]
    public BilingualString Description { get; set; }
}

public class ClassWithLongDescription
{
    [MaxLengthBilingualString(200)]
    public BilingualString Description { get; set; }
}

MaxLength 属性取决于消耗 class

MaxLength attributes depends on consuming class

c#

asp.net-mvc

maxlength

data-annotations