I\'m working on a Web API 2 project. besides the requirement that some properties are required, some only can have specific values. One option is that I could try to save the m
In case anyone stumbles upon this thread in the future, I took it a little further and added a public string array property accepting the allowable values in the validation filter. This will allow you to provide a collection of valid strings in the attribute decorator.
This way, you now have a generic reusable attribute you can use anytime to limit a model string property to a predefined set of values. Since it's a validation attribute, you can decorate it with a more informative error message as well.
Example Usage:
public class Person {
[StringRange(AllowableValues = new[] { "M", "F" }, ErrorMessage = "Gender must be either 'M' or 'F'.")]
public string Gender { get;set; }
}
String Attribute:
public class StringRangeAttribute : ValidationAttribute
{
public string[] AllowableValues { get; set; }
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
if (AllowableValues?.Contains(value?.ToString()) == true)
{
return ValidationResult.Success;
}
var msg = $"Please enter one of the allowable values: {string.Join(", ", (AllowableValues ?? new string[] { "No allowable values found" }))}.";
return new ValidationResult(msg);
}
}