Add Custom Validated with airSlate SignNow

Add custom validated

this is part 76 of asp.net code tutorial in this video we'll discuss how to create a custom validation attribute with an example out-of-the-box a spirited core provides several built-in attributes we can see some of the common ones right here for most of our application validation requirements we could use these built-in attributes we discussed using some of these built-in attributes in parts 42 and 43 of this asp.net core tutorial if you have a complex validation requirement that you cannot implement using these built-in attributes you can create a custom validation attribute and reuse it throughout your project or even in multiple projects if you create it in a separate class library project now let's understand creating a custom validation attribute with an example here is what we want to do consider this new user registration page our business requirement is to only allow email address where the domain name is presume techcom if any other domain name is used we want to display a validation error stating email domain must be presumed calm we could implement this using the built-in regular expression validator but let's create a custom validator this is the same project that we've been working with so far in this video series I'm going to add a new folder to this project we're going to place have a custom validation attribute class file in this folder let's name this folder utilities to this folder let's add a new class file let's name it valid email domain attribute to make this class a custom validation attribute we need to derive from an abstract class provided by asp.net core called validation attribute this abstract class is an system dot component model dot data annotations namespace so let's bring the ten by pressing control period next we want to override east valid method provided by this validation attribute base class notice when I type override and then we see all the methods that we can override the method that we want to override is this is valid method that takes one parameter before we implement the rest of the code let's see how we are going to use this custom validation attribute we use a custom validation attribute just like any other built-in validation attribute in our case we are going to use this custom validation attribute to validate this email field on our register view the model for this view is this register view model class and the property is email notice on this email property we are already using several built-in validation attributes in addition to these attributes we also want to use our custom validation attribute valid email domain we do not need the attribute part of the class name if you want you can include it but it's not required let's bring in the required namespace which is employee management dot utilities now what do we want this custom validation attribute to do well we wanted to validate the domain part of this provided email to be present at com what we do not want to do is hard code the domain name freedom techcom within our custom validation attribute because we want it to be reusable with any domain name so what we really want to be able to do is specify the domain name using a parameter like ha we are specifying the action name here so maybe we want a parameter called a loved domain and then we specify the domain name in this case presume techcom elsewhere in our project we could specify the domain name as google.com microsoft.com etc notice at the moment we have a red squiggly on this parameter allow domain because we do not have a constructor that takes this parameter so over obvious next step is to include a constructor within our custom validation attribute class we want to include a parameter for this constructor and the parameter name is allowed domain so let's copy it and specify it as the parameter the data type is obviously string we also need the private backing field let's generate that by pressing control period if we take a look at the register view model now notice the red squiggly is gone in addition to specifying the allowed domain name we also want to specify an error message that we want to display if the domain name is not presumed techcom we do that using the error message property at this point you might be thinking our custom validation attribute class does not have a property called error message so our obvious question is where is this property coming from well it's coming from the base class validation attribute notice when I hover the mouse over this property we can see from the intelligence the error message property is coming from validation attribute class this is a public property so if we could set a value for this property right here and the message that we want is email domain must be presumed dead calm I accidentally included a leading space in the error message we don't need that next we need to provide implementation for this is valid method notice this method has an incoming parameter where is the value for this parameter going to come from well it comes from the email input field on our switches to view because this email input field is bound to the email property in our register view model and on this email property we are using our custom validation attribute so whatever value we type in this email input field for example let's type test at test comm so this value test at tests comm will be automatically passed to the value parameter of our issue valid method notice the data type is object but we know we are expecting a string so the first thing that I'm going to do is convert the incoming value to a string next we need to retrieve the domain part from the email so from this email test a test comm we just want the domain part test com so we are going to split the string using the add character as the separator for that let's use the split method and then specify at character as the separator this split method returns a string array you can see that from the intellisense so let's create a variable of type string array let's call it strings so this strings array is going to contain two strings the first string will have the value test and the second string will have the value test calm which is the email domain and we want the email domain so to retrieve the email domain from the strings array we are going to use the index position one because arrays in dotnet are zero index based for the string comparison to be case insensitive let's convert it to the upper case next we want to compare this value with the allowed domain that is specified right here we know this value will be stored in this private field allowed the domain so let's convert that also - uppercase and then compare that this expression returns true if both the values match otherwise false so let's include the return keyword and then run this project in debug mode notice now if I try to specify a domain which is not present at comm we get our custom validation error as expected now let's change the domain name to presume techcom let's also provide the password and confirm password there we go since we have provided a valid email domain which in our case is presumed calm we have the user account successfully created in asp.net core to create a custom validation attribute create a class that derives from the built-in validation attribute class and then override is valid method we then use the custom validation attribute just like any other built-in validation attribute if the validation fails just like the built-in validation error messages our custom validation error messages are also picked up by validation tag helpers and displayed on the corresponding views we discussed validation tag helpers in detail in our previous videos in the series that's it in this video thank you for listening [Music] you