ASP.NET MVC：添加將DisplayName合併到自定義ValidationAttribute的自定義ErrorMessage

Question

我正在使用帶有DataAnnotations的ASP.NET MVC。我創建了以下自定義ValidationAttribute，它可以正常工作。

public class StringRangeAttribute : ValidationAttribute 
{ 
    public int MinLength { get; set; } 
    public int MaxLength { get; set; } 

    public StringRangeAttribute(int minLength, int maxLength) 
    { 
     this.MinLength = (minLength < 0) ? 0 : minLength; 
     this.MaxLength = (maxLength < 0) ? 0 : maxLength; 
    } 

    public override bool IsValid(object value) 
    {    
     //null or empty is <em>not</em> invalid 
     string str = (string)value; 
     if (string.IsNullOrEmpty(str)) 
      return true; 

     return (str.Length >= this.MinLength && str.Length <= this.MaxLength); 
    } 
} 

然而，出現的錯誤消息是標準的「的字段*無效」。我想將其改爲：「[DisplayName]必須介於[minlength]和[maxlength]之間」，但我無法弄清楚如何從該類中獲取DisplayName或字段的名稱。

有人知道嗎？

Answer 1

稍微修改StringLengthAttribute：

public class StringRangeAttribute : ValidationAttribute 
{ 
    // Methods 
    public StringRangeAttribute(int minimumLength, int maximumLength) 
     : base(() => "The {0} must be between {1} and {2} chars long.") 
    { 
     MaximumLength = maximumLength; 
     MinimumLength = minimumLength; 
    } 

    public override string FormatErrorMessage(string name) 
    { 
     return string.Format(CultureInfo.CurrentCulture, ErrorMessageString, new object[] { name, MinimumLength ,MaximumLength }); 
    } 

    public override bool IsValid(object value) 
    { 
     if (value != null) 
     { 
      return (((string)value).Length <= MaximumLength) && (((string)value).Length >= MinimumLength); 
     } 
     return true; 
    } 

    public int MaximumLength { get; set; } 
    public int MinimumLength { get; set; } 
}