MVC Core and EF Core manually parse date time in input text box

Question

I have a MVC core project with EF core data context. I've used scaffolding to create CRUD. I just want to know is there anyway to use my custom logic for parsing datetime in text box when the user hit save?

Currently I have this in Create page:

<div class="form-group col-md-6 col-xs-12">
    <label asp-for="Lead.BDayDateTime" class="control-label"></label>
    <input asp-for="Lead.BDayDateTime" class="form-control" />
    <span asp-validation-for="Lead.BDayDateTime" class="text-danger"></span>
</div>

and its the definition in my model:

[Required(ErrorMessage = "Please enter year of birth or birthday (ex. 1363, 1984, 1984-09-23, 1363-07-01)")]
[Display(Name = "Birthday", Prompt = "Birth Year or Birthday", Description = "Please enter year of birth or birthday (ex. 1363, 1984, 1984-09-23, 1363-07-01)")]
[DisplayFormat(NullDisplayText = "Not Entered", DataFormatString = "{0:yyyy}", ApplyFormatInEditMode = true)]
public DateTime BDayDateTime { get; set; }

I want to manually parse datetime, so the user can enter non-Gregorian datetime values (and I'll convert them to Gregorian before saving to database).

score 0 · Accepted Answer · answered Oct 16 '18 at 18:51

I found a solution to parse my custom date string to DateTime using TypeConverter:

I created a custom TypeConverter:

public class JalaliAwareDateConverter : TypeConverter
{
    public override bool CanConvertFrom(ITypeDescriptorContext context,
        Type sourceType)
    {
        if (sourceType == typeof(string))
            return true;
        return base.CanConvertFrom(context, sourceType);
    }

    public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
    {
        if (value is string s)
        {
            return s.ParseDateString(); // My custom parser
        }

        return base.ConvertFrom(context, culture, value);
    }
}

and registered it in Startup.cs (Based on my experience and thanks to this answer and @zdeněk comment, TypeConverter attribute do not work in asp.net core):

TypeDescriptor.AddAttributes(typeof(DateTime), new TypeConverterAttribute(typeof(JalaliAwareDateConverter)));

~~Now, I have valid value in DateTime property, but the validation still fails.~~ This problem was because of Regular Expression validator which was trying to validate DateTime object! Removed the regex validator and voila, it works!

score -1 · Answer 2 · answered Oct 11 '18 at 06:46

If you want to define custom validation logic, you need to create a custom class that derives from ValidationAttribute

Example code:

using System.ComponentModel.DataAnnotations;

namespace StatisticsWeb.Models
{
    public class PatientFormBirthdayValidation : ValidationAttribute
    {
        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
        {
            var patient = (Patient)validationContext.ObjectInstance;
            if (patient.BirthDate == null)
            {
                return new ValidationResult("Date of Birth field is required");
            }
            else if ((patient.BirthDate >= DateTime.Now) || (patient.BirthDate < DateTime.MinValue))
            {
                return new ValidationResult("Date of Birth is invalid");
            }
            else
            {
                return ValidationResult.Success;
            }
        }
    }
}

And decorate your model with this attribute:

[PatientFormBirthdayValidation]
public DateTime BDayDateTime { get; set; }

Of course you can use other attributes, like [Display(Name = "Date of Birth")] and [Required]

This is not what I am looking for. I actually want to change the value using my custom parser. I dont want to just validate the value. — Shahab, Oct 16 '18 at 17:52

MVC Core and EF Core manually parse date time in input text box

2 Answers2