**Course Title:** Mastering C#: From Fundamentals to Advanced Programming **Section Title:** Building Web Applications with ASP.NET Core **Topic:** Working with Razor pages and form handling **Overview** In this topic, we will explore Razor pages and how to handle forms in ASP.NET Core. Razor pages provide a simple and efficient way to create web pages that can handle user input and display data. We will cover the basics of Razor pages, including creating and binding models, validating user input, and handling form submissions. **What are Razor Pages?** Razor pages are a feature of ASP.NET Core that allows you to create web pages using a syntax similar to Razor views. However, Razor pages are designed to be more flexible and powerful than Razor views. With Razor pages, you can create reusable and self-contained pages that can handle user input and display data. **Creating a Razor Page** To create a Razor page, you need to create a new file with a `.cshtml` extension. For example, you can create a new file called `Index.cshtml` in the `Pages` folder of your project. The contents of the file should look like this: ```csharp @page @model IndexModel <h1>Welcome to my Razor page!</h1> <form method="post"> <label asp-for="Name"></label> <input asp-for="Name" type="text" /> <button type="submit">Submit</button> </form> @section Scripts { @{await Html.RenderPartialAsync("_ValidationScriptsPartial");} } ``` In this example, we have created a new Razor page called `Index.cshtml`. The `@page` directive tells ASP.NET Core that this is a Razor page. The `@model` directive specifies the model that will be used to bind data to the page. The `h1` element displays a message, and the `form` element contains a label, input field, and submit button. **Binding Models** To bind a model to a Razor page, you need to create a new class that will hold the data for the page. For example, you can create a new class called `IndexModel.cs`: ```csharp public class IndexModel : PageModel { [BindProperty] public string Name { get; set; } } ``` In this example, we have created a new class called `IndexModel` that inherits from `PageModel`. The `BindProperty` attribute is used to bind the `Name` property to the page. **Validating User Input** To validate user input, you can use data annotations on the model properties. For example, you can add a `[Required]` attribute to the `Name` property: ```csharp public class IndexModel : PageModel { [BindProperty] [Required] public string Name { get; set; } } ``` In this example, the `Name` property is now required, and ASP.NET Core will validate the input data to ensure that a value is provided. **Handling Form Submissions** To handle form submissions, you can use the `OnPost` method on the page model. For example: ```csharp public class IndexModel : PageModel { [BindProperty] [Required] public string Name { get; set; } public IActionResult OnPost() { if (!ModelState.IsValid) { return Page(); } // Handle the form submission here return RedirectToPage("Success"); } } ``` In this example, the `OnPost` method is called when the form is submitted. The method checks if the model state is valid, and if not, returns the page with errors. If the model state is valid, the method can handle the form submission and redirect to a new page. **Conclusion** In this topic, we have covered the basics of Razor pages and form handling in ASP.NET Core. We have learned how to create and bind models, validate user input, and handle form submissions. With this knowledge, you can create robust and efficient web applications using ASP.NET Core. **Additional Resources** * [Razor Pages documentation on Microsoft Docs](https://docs.microsoft.com/en-us/aspnet/core/razor-pages/) * [Data annotations on Microsoft Docs](https://docs.microsoft.com/en-us/aspnet/core/mvc/models/validation) **What's Next?** In the next topic, we will cover introduction to unit testing with NUnit or xUnit. **Leave a comment below if you have any questions or need further clarification!**