CODEWITHSUNDEEP
asp.net-mvcunobtrusive-validation
jaffa
jaffa

Reputation: 27350

What is the best way of adding a greater than 0 validator on the client-side using MVC and data annotation?

I'd like to be able to only allow a form to submit if the value in a certain field is greater than 0. I thought maybe the Mvc Range attribute would allow me to enter only 1 value to signify only a greater than test, but no luck there as it insists on Minimum AND Maximum values.

Any ideas how this can be achieved?

Upvotes: 141

Views: 148541

Answers (4)

John Lord
John Lord

Reputation: 2185

You can create your own validator like this:

    public class RequiredGreaterThanZero : ValidationAttribute
{
    /// <summary>
    /// Designed for dropdowns to ensure that a selection is valid and not the dummy "SELECT" entry
    /// </summary>
    /// <param name="value">The integer value of the selection</param>
    /// <returns>True if value is greater than zero</returns>
    public override bool IsValid(object value)
    {
        // return true if value is a non-null number > 0, otherwise return false
        int i;
        return value != null && int.TryParse(value.ToString(), out i) && i > 0;
    }
}

Then "include" that file in your model and use it as an attribute like this:

    [RequiredGreaterThanZero]
    [DisplayName("Driver")]
    public int DriverID { get; set; }

I commonly use this on dropdown validation. Note that because it's extending validationattribute you can customize the error message with a parameter.

Upvotes: 26

Greg Gum
Greg Gum

Reputation: 37939

The above validator works with integers. I extended this to work with a decimal:

    public class RequiredDecimalGreaterThanZero : ValidationAttribute
    {
        /// <summary>
        /// Designed for dropdowns to ensure that a selection is valid and not the dummy "SELECT" entry
        /// </summary>
        /// <param name="value">The integer value of the selection</param>
        /// <returns>True if value is greater than zero</returns>
        public override bool IsValid(object value)
        {
            // return true if value is a non-null number > 0, otherwise return false
            decimal i;
            return value != null && decimal.TryParse(value.ToString(), out i) && i > 0;
        }
    }

Upvotes: 1

Phil
Phil

Reputation: 1061

I found this answer looking to validate any positive value for a float/double. It turns out these types have a useful constant for 'Epsilon'

Represents the smallest positive System.Double value that is greater than zero.

    [Required]
    [Range(double.Epsilon, double.MaxValue)]
    public double Length { get; set; }

Upvotes: 39

Darin Dimitrov
Darin Dimitrov

Reputation: 1038990

You can't store a number bigger than what your underlying data type could hold so that fact that the Range attribute requires a max value is a very good thing. Remember that ∞ doesn't exist in the real world, so the following should work:

[Range(1, int.MaxValue, ErrorMessage = "Please enter a value bigger than {1}")]
public int Value { get; set; }

Upvotes: 335

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