Building a data form with validation in 3 minutes using xamarin and postsharp

Having a data form is very common in modern mobile applications , and of course in most cases you will need to validate user input before allowing him to submit the form.

In this article i will present a declarative and clean way to do the job in less then 3 minutes.

We will use syncfusion xamarin forms dataform control or any INotifyDataErrorInfo compatible data form control and Postsharp for AOP

lets start by installing postsharp visual studio extension and then create a normal xamarin forms project and install these nuget packages in the shared project:

Xamarin.Aspects.Patterns.Data.Validation 1.0.0

and

PostSharp 6.2.11

now we are ready lets create our model class

public class User {    
 public string Email { get; set; }
 public string Paswword { get; set; }
 public string ConfirmPassword { get; set; } 
}

and the validator class

public class UserValidator : AbstractValidator<User>  {
     public UserValidator()     { 
        RuleFor(u => u.Email).EmailAddress();
        RuleFor(u => u.Paswword).MinimumLength(6);  
        RuleFor(u => u.ConfirmPassword).Matches(u => u.Paswword);     } }

add the NotifyDataErrorInfo Attribute to the user class

[NotifyDataErrorInfo(typeof(UserValidator))]
public class User {    
 public string Email { get; set; }
 public string Paswword { get; set; }
 public string ConfirmPassword { get; set; } 
}

and now simply create a User object in your viewmodel and bind to the data from control as described here https://help.syncfusion.com/xamarin/sfdataform/getting-started

<?xml version="1.0" encoding="utf-8" ?> 
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" 
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:local="clr-namespace:GettingStarted"
    xmlns:dataForm="clr-namespace:Syncfusion.XForms.DataForm;assembly=Syncfusion.SfDataForm.XForms" 
x:Class="GettingStarted.MainPage"> 
<ContentPage.BindingContext>         
<local:ViewModel/>     
</ContentPage.BindingContext>  
    <dataForm:SfDataForm x:Name="dataForm" DataObject="{Binding User}"/>     
</ContentPage>

and we are done.