How to make WinForm perform Model validation?

How to make WinForm perform Model validation? If you have experience in asp.net mvc development, you will know that we can call ModelState.IsValid to verify the model. This is to verify the legality of the data submitted by the client from a security or business perspective.

Table Of Contents

1 WinForm perform Model validation

2 Validation Forms In DataAnnotations

2.1 ValidationResult

2.2 Validator class

2.3 TryValidateProperty

2.4 TryValidateValue

3 Considerations and tests

WinForm perform Model validation

For Winform development, we need to encapsulate and provide similar functions by ourselves. For Winform development, we need to encapsulate ourselves to provide similar functions. In addition, you can also find similar posts on stackoverflow. This article also shares how I did it based on these methods.For Winform development, we need to encapsulate ourselves to provide similar functions. In addition, you can also find similar posts on stackoverflow. This article also shares how I did it based on these methods.

The following content is derived from a post on c-sharpcorner.com. I think this post is very good and can help you learn some useful knowledge.

Validation Forms In DataAnnotations

In this second article, we will learn all validation forms in DataAnnotation. We will review Validator class with all its structure. The first part can be found on the following link.

DataAnnotations In Depth

DataAnnotation enables us to work with positive programming. In other words, it allows us anticipate exceptions for problems in our business classes or domain classes. It provides better performance. The negative programming version also exists.

Positive – TryValidate.
Negative – Validate.

On this link, you will get the information about Exceptions and Performance.

The examples class

The class for all examples will be a new version of the class created in part I.

public class Customer  
{  
    [Required(ErrorMessage = "{0} is mandatory")]  
    [MaxLength(50, ErrorMessage = "The {0} can not have more than {1} characters")]  
    public string Name { get; set; }  
  
    [Range(typeof(DateTime), "01/01/2016", "01/01/2050",  
        ErrorMessage = "Valid dates for the Property {0} between {1} and {2}")]  
    public DateTime EntryDate { get; set; }  
  
    public string Password { get; set; }  
  
    [Compare("Customer.Password", ErrorMessage = "The fields Password and PasswordConfirmation should be equals")]  
    public string PasswordConfirmation { get; set; }  
  
    [Range(0, 150, ErrorMessage = "The Age should be between 0 and 150 years")]  
    public int Age { get; set; }  
}

These are principal validation classes.

ValidationResult

ValidationResult is a container for class validation results. For more info, go here.

ValidationResult has 2 properties

ErrorMessages .- String readonly property with the information error description.
MemberNames.- IEnumerable<string> readonly property with the property name on error.

We have written an extension method to print the validation errors.

public static string ToDescErrorsString(this IEnumerable<ValidationResult> source, string mensajeColeccionVacia = null)  
{  
    if (source == null) throw new ArgumentNullException(nameof(source), $"The property {nameof(source)}, doesn't has null value");  
   
    StringBuilder resultado = new StringBuilder();  
   
    if (source.Count() > 0)  
    {  
        resultado.AppendLine("There are validation errors:");  
        source.ToList()  
            .ForEach(  
                s =>  
                    resultado.AppendFormat("  {0} --> {1}{2}", s.MemberNames.FirstOrDefault(), s.ErrorMessage,  
                        Environment.NewLine));  
    }  
    else  
        resultado.AppendLine(mensajeColeccionVacia ?? string.Empty);  
   
    return resultado.ToString();  
}

Validator class

This is the static helper class. The Validator class allows you to execute validation on objects, properties, and methods. You can get more information from this link.

We can separate its methods in two groups, as we saw earlier. POSITIVE PROGRAMMING (Returns bool value and we have a ICollection<ValidationResult> parameter) The return property bool is a validation result.The ICollection<ValidationResult> argument contains details of validation errors. If the validation doesn’t have errors, this collection will be empty.
TryValidateObject

public static bool TryValidateObject(object instance, ValidationContext validationContext, ICollection<ValidationResult> validationResults);  
public static bool TryValidateObject(object instance, ValidationContext validationContext, ICollection<ValidationResult> validationResults, bool validateAllProperties);

This method validates all objects. TryValidateObject has an overload with a bool argument validateAllProperties that is enabled in case when validation error continues with the validation of all properties.

Arguments

Instance The instance of class to validate.
ValidationContext The context that describes the object to validate.
ValidationResults The collection of validation results descriptions.
ValidateAllProperties Enabled continues to validate all properties.

Example

public static void TryValidateObjectExample1()  
{  
    /// 1.- Create a customer  
    var customer = new Customer  
    {  
        Name                 = string.Empty,  
        EntryDate            = DateTime.Today,  
        Password             = "AAAA",  
        PasswordConfirmation = "BBBB",  
        Age                  = -1  
    };  
    /// 2.- Create a context of validation  
    ValidationContext valContext = new ValidationContext(customer, null, null);  
    /// 3.- Create a container of results  
    var validationsResults = new List<ValidationResult>();  
    /// 4.- Validate customer  
    bool correct = Validator.TryValidateObject(customer, valContext, validationsResults, true);  
   
    Console.WriteLine(validationsResults.ToDescErrorsString("Without Errors !!!!"));  
    Console.Read();  
}

In this example, we have done the second overload with true value (ValidateAllProperties).

Result