custom validation attribute in net core

using the command line, you can run:

step 2: create a custom validation attribute

create a new class that inherits from `validationattribute` and override the `isvalid` method. in this example, we’ll create a custom validation attribute that checks if a string is not null or empty and matches a specific format.

step 3: apply the custom validation attribute to a model

now, let’s create a model where we can apply our custom validation attribute. for demonstration, we will create a simple `user` model.

step 4: create a controller

next, create a controller that will handle user input. in this example, we will create a `usercontroller` with a method to handle a post request.

step 5: configure services and add routing

step 6: test the custom validation

you can now test your custom validation by sending a post request to your api endpoint. you can use tools like postman or curl.

**example request:**

**expected response:**

if you send a valid username:

**example request:**

**expected response:**

summary

#CustomValidation #NetCore #python
Custom validation attribute
.NET Core
data annotations
validation framework
model validation
attribute validation
custom attributes
validation logic
error messaging
ASP.NET Core
user input validation
model binding
MVC validation
extensible validation
attribute-based validation