Validation of double using System.Configuration validator

Question

I had to create a custom configuration section for my library. One of the parameters in the configuration should be positive double. However, for some reason I could not find any Validator for double.

For instance, here's how I use the integer validator:

[ConfigurationProperty("someProp", IsRequired = false, DefaultValue = 15)]
[IntegerValidator(MaxValue = 200, MinValue = 0)]
public int SomeProperty
{
   get
   {
      return (int)this["someProp"];
   }
   set
   {
      this["someProp"] = value;
   }
}

I've looked through Google and was not able to find any mention of DoubleValidator or FloatValidator. Is it possible to somehow make sure the property is a positive double? Are there any reasons DoubleValidator is not present in the System.Configuration? Maybe I am mistaken and double properties should not be stored in the config file.

Have a look at my question here: stackoverflow.com/questions/39348791/… — Morten Toudahl
– Morten Toudahl, Commented Sep 8, 2016 at 8:08
@MortenToudahl Thanks, looks like it might be the thing I needed back then. I hardly need it anymore, but thank you anyway. — Vlad Stryapko
– Vlad Stryapko, Commented Sep 8, 2016 at 9:34
Yea, i was actually going to post it here as an answer. But then i ran into the default value problem :) — Morten Toudahl
– Morten Toudahl, Commented Sep 8, 2016 at 11:27

Community · Accepted Answer · 2017-05-23 12:08:23Z

I needed a float validator for my own project, and found your question. This is how I made my validator. When/if you use it, you should remember to set a default value on the ConfigurationPropertyAttribute that you annotate the property with.

Thanks to Kasper Videbæk for finding my mistake: ConfigurationValidatorBase validate method receives default value

class DoubleValidator : ConfigurationValidatorBase
{
    public double MinValue { get; private set; }
    public double MaxValue { get; private set; }

    public DoubleValidator(double minValue, double maxValue)
    {
        MinValue = minValue;
        MaxValue = maxValue;
    }

    public override bool CanValidate(Type type)
    {
        return type == typeof(double);
    }

    public override void Validate(object obj)
    {
        double value;
        try
        {
            value = Convert.ToDouble(obj);
        }
        catch (Exception)
        {
            throw new ArgumentException();
        }

        if (value < MinValue)
        {
            throw new ConfigurationErrorsException($"Value too low, minimum value allowed: {MinValue}");
        }

        if (value > MaxValue)
        {
            throw new ConfigurationErrorsException($"Value too high, maximum value allowed: {MaxValue}");
        }
    }
}

The attribute to use on the configurationproperty

class DoubleValidatorAttribute : ConfigurationValidatorAttribute
{
    public double MinValue { get; set; }
    public double MaxValue { get; set; }

    public DoubleValidatorAttribute(double minValue, double maxValue)
    {
        MinValue = minValue;
        MaxValue = maxValue;
    }

    public override ConfigurationValidatorBase ValidatorInstance => new DoubleValidator(MinValue, MaxValue);
}

Community · Accepted Answer · 2017-05-23 12:32:45Z

-1

You could try RangeValidator. Something like

[Range(0,double.MaxValue, ErrorMessage = "Number must be positive. ")]
public float someProperty (...) { ...}

You can see this SO answer for more examples https://stackoverflow.com/a/17164247 .

edited May 23, 2017 at 12:32

CommunityBot

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answered Nov 27, 2015 at 16:14

OscuroAA

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1 Comment

CodeCaster Over a year ago

The System.ComponentModel.DataAnnotations attributes are validation attributes for systems that support it. Not relevant at all to custom configuration sections. Remember that an attribute does nothing of itself: the code handling the attributed type does. And ConfigurationSectionHandler does nothing with the RangeAttribute.

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