how to validate phone number that is already exist in table

Question

Hi, How to show error message when enter already exist phone number during registeration(MVC). Thank You.

Sachin Singh · Answer

step 1. Create a class PhoneNumberCheck overriding validationAttribute as shown below public class PhoneNumberCheck:ValidationAttribute { protected override ValidationResult IsValid(object value, ValidationContext validationContext) { int [] phones= context.UserMaster.Select(x=>x.Phone).ToArray(); UserMaster user= (UserMaster)validationContext.ObjectInstance; bool istrue = phones.Any(x => x == user.Phone); if (istrue) { return new ValidationResult( "Phone is in use" ); } return ValidationResult.Success; } } step 2. user this attribute on UserMaster class public class UserMaster { [Required(ErrorMessage= "can not be empty" )] public string Name { get; set; } [Required] [Range(18,45,ErrorMessage= "Age must be between 18 and 45" )] public int Age { get; set; } [DataType(DataType.EmailAddress)] public string Email { get; set; } [DataType(DataType.PhoneNumber)] [ PhoneNumberCheck ] public int Phone { get; set; } } Now, you will get the error message if the phone number exist. please refer to my article on this https://www.sharpencode.com/article/MVC/data-annotations

Sachin Singh · Answer

context is EntityFramework's context object if you are using ado.net then accordingly retrieve all the phone number from database.

Sachin Singh · Answer

UserMaster is the table in the database and class in the model.

vijayaasri palaniappan · Answer

Hi, Yeah! I changed that.Then for Context ??

Kapil Gaur · Answer

Very good Sachin you have explained with quality code. This shows how dedicatedly you help people. I would just add here one thing this is the code where we have considered the data annotation validations and we have considered the list of numbers available in your project. Similarly you can also create remote repository validation also where again you will send that number to another API and it will give you the result. So there are n possible ways but Sachin has explained the best possible way. you can tweak a little bit always as per requirements.

vijayaasri palaniappan · Answer

Hi Sachin, It shows error in UserMaster and Context. Thank you.